Plumbing for e2e pings. (#1973)

* Plumbing for e2e pings.
* linter fixes
* Re-use existing event instead of introducing a new one.

JitsiConference.js

     this.xmpp = this.connection?.xmpp;
 
     if (this.xmpp.isRoomCreated(options.name, options.customDomain)) {
-        const errmsg = 'A coference with the same name has already been created!';
+        const errmsg = 'A conference with the same name has already been created!';
 
         delete this.connection;
         delete this.xmpp;

modules/e2eping/e2eping.js

 import { getLogger } from '@jitsi/logger';
 
 import * as JitsiConferenceEvents from '../../JitsiConferenceEvents';
+import * as JitsiE2EPingEvents from '../../service/e2eping/E2ePingEvents';
 
 const logger = getLogger(__filename);
 
             logger.info(`Measured RTT=${rtt} ms to ${this.id} (in ${this.participant.getProperty('region')})`);
             this.stop();
 
+            this.e2eping.conference.eventEmitter.emit(
+                JitsiE2EPingEvents.E2E_RTT_CHANGED, this.participant, rtt);
+
             return;
         } else if (totalNumRequests > 2 * this.e2eping.numRequests) {
             logger.info(`Stopping e2eping for ${this.id} because we sent ${totalNumRequests} with only `