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/db/TimelineDaoTest.kt

@@ -463,6 +463,7 @@ class TimelineDaoTest {
             contentShowing = true,
             pinned = false,
             card = card,
+            language = null,
         )
         return Triple(status, author, reblogAuthor)
     }