Enable Offline mode of the SyncService, so that the sync starts automatically when the network is back.

Also rely on the sync state to render the "Offline" banner.

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/sync/SyncState.kt

@@ -14,3 +14,11 @@ enum class SyncState {
     Terminated,
     Offline,
 }
+
+fun SyncState.isConnected() = when (this) {
+    SyncState.Idle,
+    SyncState.Running,
+    SyncState.Error,
+    SyncState.Terminated -> true
+    SyncState.Offline -> false
+}