add ktlint plugin to project and apply default code style (#2209)

* add ktlint plugin to project and apply default code style

* some manual adjustments, fix wildcard imports

* update CONTRIBUTING.md

* fix formatting

app/src/main/java/com/keylesspalace/tusky/service/ServiceClient.kt

@@ -31,4 +31,4 @@ class ServiceClientImpl(private val context: Context) : ServiceClient {
             context.startService(intent)
         }
     }
-}
+}