Merge commit '44cd88adc4e2f4028dcc2b08b98368f0dc90cee4' into glitch-soc/merge-upstream

Conflicts:
- `.github/dependabot.yml`:
  Updated upstream, but we've deleted it.
  Keep it deleted.
- `app/javascript/mastodon/locales/index.js`:
  Reworked upstream, but the code was mostly in
  `app/javascript/locales/index.js` in glitch-soc.
  Updated that file accordingly.
- `app/javascript/packs/public.jsx`:
  Not a real conflict, but different imports in
  glitch-soc and upstream.
- `app/views/layouts/application.html.haml`:
  Conflict due to locales loading and theme system
  discrepancies.
  Updated in our own way.
- `app/views/layouts/embedded.html.haml`:
  Conflict due to locales loading and theme system
  discrepancies.
  Updated in our own way.
- `config/webpack/generateLocalePacks.js`:
  Deleted upstream, as upstream now directly loads the
  JSON at runtime.
  Deleted as well, will switch to runtime loading in
  an upcoming commit.
- `config/webpack/shared.js`:
  Not a real conflict, but different imports in
  glitch-soc and upstream.
- `config/webpack/translationRunner.js`:
  Mostly deleted upstream, to be replaced with `formatjs-formatter.js`
  instead.
  Moved the glitch-soc logic there and deleted the file.

app/views/layouts/application.html.haml

@@ -29,9 +29,9 @@
     = javascript_pack_tag "locales", crossorigin: 'anonymous'
     - if @theme
       - if @theme[:supported_locales].include? I18n.locale.to_s
-        = javascript_pack_tag "locales/#{@theme[:flavour]}/#{I18n.locale}", crossorigin: 'anonymous'
+        = preload_pack_asset "locales/#{@theme[:flavour]}/#{I18n.locale}-json.js"
       - elsif @theme[:supported_locales].include? 'en'
-        = javascript_pack_tag "locales/#{@theme[:flavour]}/en", crossorigin: 'anonymous'
+        = preload_pack_asset "locales/#{@theme[:flavour]}/en-json.js"
     = csrf_meta_tags unless skip_csrf_meta_tags?
     %meta{ name: 'style-nonce', content: request.content_security_policy_nonce }