Allow creating knock rooms (#11182)

Signed-off-by: Charly Nguyen <charly.nguyen@nordeck.net>

src/utils/PreferredRoomVersions.ts

@@ -23,6 +23,11 @@ limitations under the License.
  * Loosely follows https://spec.matrix.org/latest/rooms/#feature-matrix
  */
 export class PreferredRoomVersions {
+    /**
+     * The room version to use when creating "knock" rooms.
+     */
+    public static readonly KnockRooms = "7";
+
     /**
      * The room version to use when creating "restricted" rooms.
      */