feat(transcription): Add transcription status

JitsiConference.js

     return this.transcriber;
 };
 
+/**
+ * Returns the transcription status.
+ *
+ * @returns {String} "on" or "off".
+ */
+JitsiConference.prototype.getTranscriptionStatus = function() {
+    return this.room.transcriptionStatus;
+};
+
 /**
  * Adds JitsiLocalTrack object to the conference.
  * @param track the JitsiLocalTrack object.

JitsiConferenceEventManager.js

     this.chatRoomForwarder.forward(XMPPEvents.RECORDER_STATE_CHANGED,
         JitsiConferenceEvents.RECORDER_STATE_CHANGED);
 
+    this.chatRoomForwarder.forward(XMPPEvents.TRANSCRIPTION_STATUS_CHANGED,
+        JitsiConferenceEvents.TRANSCRIPTION_STATUS_CHANGED);
+
     this.chatRoomForwarder.forward(XMPPEvents.VIDEO_SIP_GW_AVAILABILITY_CHANGED,
         JitsiConferenceEvents.VIDEO_SIP_GW_AVAILABILITY_CHANGED);
 

JitsiConferenceEvents.js

  */
 export const TRACK_REMOVED = 'conference.trackRemoved';
 
+/**
+ * Notifies for transcription status changes. The event provides the
+ * following parameters to its listeners:
+ *
+ * @param {String} status - The new status.
+ */
+export const TRANSCRIPTION_STATUS_CHANGED
+    = 'conference.transcriptionStatusChanged';
+
+
 /**
  * A new user joinned the conference.
  */

JitsiMeetJS.js

 import JitsiTrackError from './JitsiTrackError';
 import * as JitsiTrackErrors from './JitsiTrackErrors';
 import * as JitsiTrackEvents from './JitsiTrackEvents';
+import * as JitsiTranscriptionStatus from './JitsiTranscriptionStatus';
 import LocalStatsCollector from './modules/statistics/LocalStatsCollector';
 import Recording from './modules/xmpp/recording';
 import Logger from 'jitsi-meet-logger';
         participantConnectionStatus: ParticipantConnectionStatus,
         recordingStatus: Recording.status,
         recordingTypes: Recording.types,
-        sipVideoGW: VideoSIPGWConstants
+        sipVideoGW: VideoSIPGWConstants,
+        transcriptionStatus: JitsiTranscriptionStatus
     },
     events: {
         conference: JitsiConferenceEvents,

JitsiTranscriptionStatus.js

+/**
+ * The transciption is on.
+ *
+ * @type {String}
+ */
+export const ON = 'on';
+
+/**
+ * The transciption is off.
+ *
+ * @type {String}
+ */
+export const OFF = 'off';

modules/xmpp/ChatRoom.js

 /* global $, $pres, $iq, $msg, __filename, Strophe */
 import { getLogger } from 'jitsi-meet-logger';
 import GlobalOnErrorHandler from '../util/GlobalOnErrorHandler';
+import * as JitsiTranscriptionStatus from '../../JitsiTranscriptionStatus';
 import Listenable from '../util/Listenable';
 import * as MediaType from '../../service/RTC/MediaType';
 import Moderator from './moderator';
         this.participantPropertyListener = null;
 
         this.locked = false;
+        this.transcriptionStatus = JitsiTranscriptionStatus.OFF;
     }
 
     /* eslint-enable max-params */
             case 'jibri-recording-status':
                 jibri = node;
                 break;
+            case 'transcription-status': {
+                const { attributes } = node;
+
+                if (!attributes) {
+                    break;
+                }
+
+                const { status } = attributes;
+
+                if (status && status !== this.transcriptionStatus) {
+                    this.transcriptionStatus = status;
+                    this.eventEmitter.emit(
+                        XMPPEvents.TRANSCRIPTION_STATUS_CHANGED,
+                        status
+                    );
+                }
+
+
+                break;
+            }
             case 'call-control': {
                 const att = node.attributes;
 

service/xmpp/XMPPEvents.js

     // suspending detected
     SUSPEND_DETECTED: 'xmpp.suspend_detected',
 
+    /**
+     * Notifies for transcription status changes. The event provides the
+     * following parameters to its listeners:
+     *
+     * @param {String} status - The new status.
+     */
+    TRANSCRIPTION_STATUS_CHANGED: 'xmpp.transcription_status_changed',
+
     /**
      * Event fired when 'transport-info' with new ICE candidates is received.
      */