feat: Implement sub-room functionality

- Added support for sub-rooms in the SpaceHierarchy component, allowing rooms to have nested child rooms.
- Introduced UnjoinedSubRoomItem component to display unjoined sub-rooms with a join button.
- Created SubRooms settings page for managing sub-rooms, including adding and removing sub-rooms.
- Updated RoomNavItem to include options for creating sub-rooms.
- Enhanced room fetching logic to filter out sub-rooms from the main room list.
- Added hooks for managing sub-rooms state and permissions.
- Updated relevant state management to handle sub-room creation and association with parent rooms.

src/app/state/roomSettings.ts

@@ -4,6 +4,7 @@ export enum RoomSettingsPage {
   GeneralPage,
   MembersPage,
   PermissionsPage,
+  SubRoomsPage,
   EmojisStickersPage,
   DeveloperToolsPage,
 }