feat(lobby) Add sound for participant knocking

react/features/lobby/constants.js

  * Hide these emails when trying to join a lobby
  */
 export const HIDDEN_EMAILS = [ 'inbound-sip-jibri@jitsi.net', 'outbound-sip-jibri@jitsi.net' ];
+
+/**
+ * The identifier of the sound to be played when a participant joins lobby.
+ * @type {string}
+ */
+export const KNOCKING_PARTICIPANT_SOUND_ID = 'KNOCKING_PARTICIPANT_SOUND';

react/features/lobby/middleware.js

 // @flow
 
+import { batch } from 'react-redux';
+
+import { APP_WILL_MOUNT, APP_WILL_UNMOUNT } from '../base/app';
 import { CONFERENCE_FAILED, CONFERENCE_JOINED } from '../base/conference';
 import { JitsiConferenceErrors, JitsiConferenceEvents } from '../base/lib-jitsi-meet';
 import { getFirstLoadableAvatarUrl, getParticipantDisplayName } from '../base/participants';
 import { MiddlewareRegistry, StateListenerRegistry } from '../base/redux';
+import { playSound, registerSound, unregisterSound } from '../base/sounds';
 import { isTestModeEnabled } from '../base/testing';
 import { NOTIFICATION_TYPE, showNotification } from '../notifications';
 import { shouldAutoKnock } from '../prejoin/functions';
     startKnocking,
     setPasswordJoinFailed
 } from './actions';
+import { KNOCKING_PARTICIPANT_SOUND_ID } from './constants';
+import { KNOCKING_PARTICIPANT_FILE } from './sounds';
 
 MiddlewareRegistry.register(store => next => action => {
     switch (action.type) {
+    case APP_WILL_MOUNT:
+        store.dispatch(registerSound(KNOCKING_PARTICIPANT_SOUND_ID, KNOCKING_PARTICIPANT_FILE));
+        break;
+    case APP_WILL_UNMOUNT:
+        store.dispatch(unregisterSound(KNOCKING_PARTICIPANT_SOUND_ID));
+        break;
     case CONFERENCE_FAILED:
         return _conferenceFailed(store, next, action);
     case CONFERENCE_JOINED:
             });
 
             conference.on(JitsiConferenceEvents.LOBBY_USER_JOINED, (id, name) => {
-                dispatch(participantIsKnockingOrUpdated({
-                    id,
-                    name
-                }));
+                batch(() => {
+                    dispatch(participantIsKnockingOrUpdated({
+                        id,
+                        name
+                    }));
+                    dispatch(playSound(KNOCKING_PARTICIPANT_SOUND_ID));
+                });
             });
 
             conference.on(JitsiConferenceEvents.LOBBY_USER_UPDATED, (id, participant) => {

react/features/lobby/sounds.js

+/**
+ * The name of the bundled sound file which will be played when a
+ * participant enters lobby.
+ */
+export const KNOCKING_PARTICIPANT_FILE = 'knock.mp3';