Merge commit '3f6887557b23d363e7f8f18518db4447739d64bb' into glitch-soc/merge-upstream

Conflicts:
- `app/javascript/entrypoints/common.js`:
  Upstream moved everything from `app/javascript/packs` to
  `app/javascript/entrypoints` while this file was a glitch-soc
  addition. Moved it like the rest.
- `tsconfig.json`:
  Conflict due to glitch-soc's flavor.
  Updated like upstream.

Also moved and updated the following files accordingly:
- `app/javascript/flavours/vanilla/theme.yml`
- `app/javascript/flavours/glitch/theme.yml`
- everything in `app/javascript/flavours/glitch/packs`

app/javascript/entrypoints/common.js

@@ -0,0 +1,5 @@
+/* This file is a hack to have something more reliable than the upstream `common` tag
+  that is implicitly generated as the common chunk through webpack's `splitChunks` config */
+
+import './public-path';
+import 'font-awesome/css/font-awesome.css';