Add language dropdown to compose view (#2651)

* Add UI for selecting post language

* Apply selected language when sending status

* Save/restore post language with drafts

* Fall back to english if the configured language isn't found in the locale list (no-NB)

* Remove comment about no_NB

* Move language dropdown to top of compose view

* Preserve language when redrafting

* Set default language to target post's language when replying

* Add Tusky license header to new source file

* Tweak language dropdown button width

app/src/main/java/com/keylesspalace/tusky/db/DraftEntity.kt

@@ -40,6 +40,7 @@ data class DraftEntity(
     val poll: NewPoll?,
     val failedToSend: Boolean,
     val scheduledAt: String?,
+    val language: String?,
 )
 
 /**