Implement Polish translation (#6283)

* Initial polish translation sweep

* rewrite feeds page flavor text

* bring up to date with dev branch, revisit some strings

* redoing some more...

* bring up to date

* rm dead strings, try out a different phrasing for threaded mode str

prev translation was nonsensical - we're already calling threads "wątki". let's try "recursive tree" instead to describe what threaded mode does

* tweaks here and there

* more tweaks. sign translation file

TL note: trying a new space-saving translation for send via direct message, old one made the context menu stretch

* space-saving translations for profile tabs

* up to date

* tl latest changes

* some small fixes

* few more tweaks around profile editing strings

* i dislike gendered languages

* yet more tweaks

* Update dates.ts

* Review suggestions (1)

* tiny fixes

* Review suggestions (2)

* Review suggestions (3)

* Review suggestions (4)

* "Anuluj wyciszenie"

* A few new strings

* Remove dead strings again

* Review suggestions (5)

* te -> to

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Co-authored-by: Frudrax Cheng <i@cynosura.one>

src/locale/helpers.ts

@@ -145,6 +145,8 @@ export function sanitizeAppLanguageSetting(appLanguage: string): AppLanguage {
         return AppLanguage.ja
       case 'ko':
         return AppLanguage.ko
+      case 'pl':
+        return AppLanguage.pl
       case 'pt-BR':
         return AppLanguage.pt_BR
       case 'ru':