Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- `README.md`:
  Our README.md files are completely different. Discarded upstream changes.
- `app/javascript/core/admin.js`:
  Updating rails-ujs, no real conflict, but a comment to close to changed
  code. Various glitch-soc-only files have been updated to match those changes,
  though.
- `package.json`:
  No real conflict, just an additional dependency in glitch-soc that was too
  close to something updated upstream. Took upstream's changes.

app/lib/language_detector.rb

@@ -52,8 +52,10 @@ class LanguageDetector
 
   def detect_language_code(text)
     return if unreliable_input?(text)
+
     result = @identifier.find_language(text)
-    iso6391(result.language.to_s).to_sym if result.reliable?
+
+    iso6391(result.language.to_s).to_sym if result&.reliable?
   end
 
   def iso6391(bcp47)