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/entity/NewStatus.kt

@@ -27,7 +27,8 @@ data class NewStatus(
     val sensitive: Boolean,
     @SerializedName("media_ids") val mediaIds: List<String>?,
     @SerializedName("scheduled_at") val scheduledAt: String?,
-    val poll: NewPoll?
+    val poll: NewPoll?,
+    val language: String?,
 )
 
 @Parcelize