viewer: migrate to vue 3, general refactoring and cleanup

Non-exhaustive list of fixes and improvements done at the same time:

- html default background to grey (avoids white flash during init)
- unified links behavior
- added more theme variables
- removed the flex-expand transition (it wasn't working) and replaced it
  with a slide
- fixed LdLoading not centered on the content
- title on removable tags
- fixed an issue with encoded URI from vue-router
- unified Item resource URLs
- removed the iframe for PlainTextViewer (it wasn't working properly)
  and replaced it with a pre
- fixed clear and search buttons tabindex
- fixed the information panel bumping up during the fade animation of
  tag's dropdown
- fixed some focus outlines not appearing correctly
- moved CSS variables to the :root context
- Code cleaning

GitHub: closes #217
GitHub: closes #300
GitHub: closes #297
GitHub: closes #105
GitHub: closes #267
GitHub: closes #275
GitHub: closes #228
GitHub: closes #215
GitHub: closes #112

8 files changed, 516 insertions, 0 deletions

diff --git a/viewer/src/views/item_handlers/AudioViewer.vue b/viewer/src/views/item_handlers/AudioViewer.vue
new file mode 100644
index 0000000..da9579f
--- /dev/null
+++ b/viewer/src/views/item_handlers/AudioViewer.vue
@@ -0,0 +1,65 @@
+<!--
+-- ldgallery - A static generator which turns a collection of tagged
+--             pictures into a searchable web gallery.
+--
+-- Copyright (C) 2020  Pacien TRAN-GIRARD
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as
+-- published by the Free Software Foundation, either version 3 of the
+-- License, or (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <https://www.gnu.org/licenses/>.
+-->
+
+<template>
+  <div class="flex-column container-vh-centering">
+    <ItemThumbnail :item="item" />
+    <audio
+      :class="$style.player"
+      :src="itemResourceUrl"
+      preload="auto"
+      controls
+    >
+      <a
+        :download="itemFileName"
+        :href="itemResourceUrl"
+        v-text="t('download.download-file-fmt', [itemFileName])"
+      />
+    </audio>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { AudioItem } from '@/@types/gallery';
+import { useNavigation } from '@/services/navigation';
+import { useItemResource } from '@/services/ui/ldItemResourceUrl';
+import { computed, PropType } from 'vue';
+import { useI18n } from 'vue-i18n';
+import ItemThumbnail from '../ItemThumbnail.vue';
+
+const props = defineProps({
+  item: { type: Object as PropType<AudioItem>, required: true },
+});
+
+const { t } = useI18n();
+const navigation = useNavigation();
+
+const { itemResourceUrl } = useItemResource(props.item);
+const itemFileName = computed(() => navigation.getFileName(props.item));
+</script>
+
+<style lang="scss" module>
+.player {
+  width: 100%;
+  max-width: 500px;
+  margin-top: 1em;
+  text-align: center; // for fallback download link
+}
+</style>
diff --git a/viewer/src/views/item_handlers/DirectoryViewer.vue b/viewer/src/views/item_handlers/DirectoryViewer.vue
new file mode 100644
index 0000000..9b52fa8
--- /dev/null
+++ b/viewer/src/views/item_handlers/DirectoryViewer.vue
@@ -0,0 +1,42 @@
+<!-- ldgallery - A static generator which turns a collection of tagged
+--             pictures into a searchable web gallery.
+--
+-- Copyright (C) 2019-2022  Guillaume FOUET
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as
+-- published by the Free Software Foundation, either version 3 of the
+-- License, or (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <https://www.gnu.org/licenses/>.
+-->
+
+<template>
+  <GalleryTiles
+    :items="props.item.properties.items"
+    :noresult-message="t('directory.no-results')"
+  />
+</template>
+
+<script setup lang="ts">
+import { DirectoryItem } from '@/@types/gallery';
+import { useUiStore } from '@/store/uiStore';
+import GalleryTiles from '@/views/GalleryTiles.vue';
+import { PropType } from 'vue';
+import { useI18n } from 'vue-i18n';
+
+const props = defineProps({
+  item: { type: Object as PropType<DirectoryItem>, required: true },
+});
+
+const { t } = useI18n();
+const uiStore = useUiStore();
+
+uiStore.toggleFullscreen(false);
+</script>
diff --git a/viewer/src/views/item_handlers/DownloadViewer.vue b/viewer/src/views/item_handlers/DownloadViewer.vue
new file mode 100644
index 0000000..6562bee
--- /dev/null
+++ b/viewer/src/views/item_handlers/DownloadViewer.vue
@@ -0,0 +1,66 @@
+<!--
+-- ldgallery - A static generator which turns a collection of tagged
+--             pictures into a searchable web gallery.
+--
+-- Copyright (C) 2020  Pacien TRAN-GIRARD
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as
+-- published by the Free Software Foundation, either version 3 of the
+-- License, or (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <https://www.gnu.org/licenses/>.
+-->
+
+<template>
+  <div class="container-vh-centering">
+    <a
+      :class="$style.content"
+      :download="itemFileName"
+      :href="itemResourceUrl"
+    >
+      <!-- TODO: show thumbnail instead of this generic file download icon? -->
+      <fa-icon
+        :class="$style.icon"
+        :icon="faFileDownload"
+        size="6x"
+      />
+      <div>{{ t("download.download-file-fmt", [itemFileName]) }}</div>
+    </a>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { DownloadableItem } from '@/@types/gallery';
+import { useNavigation } from '@/services/navigation';
+import { useItemResource } from '@/services/ui/ldItemResourceUrl';
+import { faFileDownload } from '@fortawesome/free-solid-svg-icons';
+import { computed, PropType } from 'vue';
+import { useI18n } from 'vue-i18n';
+
+const props = defineProps({
+  item: { type: Object as PropType<DownloadableItem>, required: true },
+});
+
+const { t } = useI18n();
+const navigation = useNavigation();
+
+const itemFileName = computed(() => navigation.getFileName(props.item));
+const { itemResourceUrl } = useItemResource(props.item);
+</script>
+
+<style lang="scss" module>
+.content {
+  text-align: center;
+}
+
+.icon {
+  margin-bottom: 0.15em;
+}
+</style>
diff --git a/viewer/src/views/item_handlers/MarkdownViewer.vue b/viewer/src/views/item_handlers/MarkdownViewer.vue
new file mode 100644
index 0000000..d5ac7e2
--- /dev/null
+++ b/viewer/src/views/item_handlers/MarkdownViewer.vue
@@ -0,0 +1,50 @@
+<!--
+-- ldgallery - A static generator which turns a collection of tagged
+--             pictures into a searchable web gallery.
+--
+-- Copyright (C) 2021  Guillaume FOUET
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as
+-- published by the Free Software Foundation, either version 3 of the
+-- License, or (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <https://www.gnu.org/licenses/>.
+-->
+
+<template>