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

1 files changed, 33 insertions, 7 deletions

diff --git a/viewer/src/assets/scss/transition.scss b/viewer/src/assets/scss/transition.scss
index fb8d2af..49fd5ba 100644
--- a/viewer/src/assets/scss/transition.scss
+++ b/viewer/src/assets/scss/transition.scss
@@ -17,16 +17,42 @@
 -- along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
-@import "~@/assets/scss/theme.scss";
+@import "theme";
 
 // === Transitions for Vue
 
-.flex-expand-enter-active, .flex-expand-leave-active {
-  transition: max-height $transition-flex-expand linear;
+// slide
+.slide-enter-active, 
+.slide-leave-active {
+  transition: transform $transition-slide linear;
 }
-.flex-expand-enter, .flex-expand-leave-to {
-  max-height: 0%;
+.slide-enter-from, 
+.slide-leave-to {
+  transform: translateX(-100%);
 }
-.flex-expand-enter-to, .flex-expand-leave {
-  max-height: 100%;
+
+// fade
+.fade-enter-active,
+.fade-leave-active {
+  transition: opacity $transition-fade ease;
+}
+
+.fade-enter-from,
+.fade-leave-to {
+  opacity: 0;
+}
+
+// moving
+.move-move,
+.move-enter-active,
+.move-leave-active {
+  transition: all $transition-move ease-in-out;
+}
+.move-enter-from,
+.move-leave-to {
+  opacity: 0;
+  transform: translateX(15px);
 }
+.move-leave-active {
+  position: absolute;
+}
\ No newline at end of file