feat: added group_admin_changed event (#2018)

* docs: updated

* added group-admin-change event

* minor changes

* added usage example

* minor changes: code docs updated

src/Client.js

@@ -45,6 +45,7 @@ const NoAuth = require('./authStrategies/NoAuth');
  * @fires Client#group_update
  * @fires Client#disconnected
  * @fires Client#change_state
+ * @fires Client#group_admin_changed
  */
 class Client extends EventEmitter {
     constructor(options = {}) {
@@ -317,6 +318,13 @@ class Client extends EventEmitter {
                      * @param {GroupNotification} notification GroupNotification with more information about the action
                      */
                     this.emit(Events.GROUP_LEAVE, notification);
+                } else if (msg.subtype === 'promote' || msg.subtype === 'demote') {
+                    /**
+                     * Emitted when a current user is promoted to an admin or demoted to a regular user.
+                     * @event Client#group_admin_changed
+                     * @param {GroupNotification} notification GroupNotification with more information about the action
+                     */
+                    this.emit(Events.GROUP_ADMIN_CHANGED, notification);
                 } else {
                     /**
                      * Emitted when group settings are updated, such as subject, description or picture.

src/util/Constants.js

@@ -46,6 +46,7 @@ exports.Events = {
     MEDIA_UPLOADED: 'media_uploaded',
     GROUP_JOIN: 'group_join',
     GROUP_LEAVE: 'group_leave',
+    GROUP_ADMIN_CHANGED: 'group_admin_changed',
     GROUP_UPDATE: 'group_update',
     QR_RECEIVED: 'qr',
     LOADING_SCREEN: 'loading_screen',