Adding isSharingScreen() to external API

modules/API/external/external_api.js

@@ -760,6 +760,17 @@ export default class JitsiMeetExternalAPI extends EventEmitter {
         });
     }
 
+    /**
+     * Returns screen sharing status.
+     *
+     * @returns {Promise} - Resolves with screensharing status and rejects on failure.
+     */
+    isSharingScreen() {
+        return this._transport.sendRequest({
+            name: 'is-sharing-screen'
+        });
+    }
+
     /**
      * Returns the avatar URL of a participant.
      *