Add Joined devices dialogue and version notices

src/serviceFeatures/joinedDevicesCommand.ts

@@ -0,0 +1,5 @@
+import { declareUICommand } from "@vrtmrz/livesync-commonlib/ui-commands";
+
+export const OPEN_JOINED_DEVICES = declareUICommand<void, "closed" | "already-open" | "unavailable">(
+    "livesync:joined-devices"
+);