Add Real-Time Listeners for Group Creation, Update, and Deletion in CometChat SDK/API

Currently, when using the CometChat SDK or API to create, update, or delete groups, these changes are not reflected in real-time for other users. Developers need to manually refresh or fetch the group data to see updates, which impacts user experience and real-time collaboration.

Having dedicated listeners for group events—such as onGroupCreated, onGroupUpdated, and onGroupDeleted—would allow the app to automatically update the UI in real-time whenever a group is created, modified, or removed. This would greatly enhance the responsiveness and interactivity of applications using CometChat.