[APP-718] Improvements and fixes to language handling (#931)

* Add locale helpers for narrowing languages

* Add a translate link to posts in a different language

* Update language filtering to use narrowing when multiple declared

* Fix a few more RTL layout cases

* Fix types

src/locale/languages.ts

@@ -555,3 +555,7 @@ export const LANGUAGES_MAP_CODE2 = Object.fromEntries(
 export const LANGUAGES_MAP_CODE3 = Object.fromEntries(
   LANGUAGES.map(lang => [lang.code3, lang]),
 )
+// some additional manual mappings (not clear if these should be in the "official" mappings)
+if (LANGUAGES_MAP_CODE2.fa) {
+  LANGUAGES_MAP_CODE3.pes = LANGUAGES_MAP_CODE2.fa
+}