Add event type string

Signed-off-by: RMidhunSuresh <rmidhunsuresh@gmail.com>

src/matrix/room/timeline/PowerLevels.js

@@ -14,6 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+export const EVENT_TYPE = "m.room.power_levels";
+
 export class PowerLevels {
     constructor({powerLevelEvent, createEvent, ownUserId, membership}) {
         this._plEvent = powerLevelEvent;