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/test/java/com/keylesspalace/tusky/BottomSheetActivityTest.kt

@@ -88,7 +88,8 @@ class BottomSheetActivityTest {
         pinned = false,
         muted = false,
         poll = null,
-        card = null
+        card = null,
+        language = null,
     )
     private val statusSingle = Single.just(SearchResult(emptyList(), listOf(status), emptyList()))