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/javascript/locales/index.js

@@ -7,3 +7,16 @@ export function setLocale(locale) {
 export function getLocale() {
   return theLocale;
 }
+
+export function onProviderError(error) {
+  // Silent the error, like upstream does
+  if(process.env.NODE_ENV === 'production') return;
+
+  // This browser does not advertise Intl support for this locale, we only print a warning
+  // As-per the spec, the browser should select the best matching locale
+  if(typeof error === "object" && error.message.match("MISSING_DATA")) {
+    console.warn(error.message);
+  }
+
+  console.error(error);
+}