feat: widget opened and closed events (#11240)

Fixes #9272

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

app/javascript/sdk/IFrameHelper.js

@@ -22,7 +22,11 @@ import {
 } from './bubbleHelpers';
 import { isWidgetColorLighter } from 'shared/helpers/colorHelper';
 import { dispatchWindowEvent } from 'shared/helpers/CustomEventHelper';
-import { CHATWOOT_ERROR, CHATWOOT_READY } from '../widget/constants/sdkEvents';
+import {
+  CHATWOOT_ERROR,
+  CHATWOOT_POSTBACK,
+  CHATWOOT_READY,
+} from '../widget/constants/sdkEvents';
 import { SET_USER_ERROR } from '../widget/constants/errorTypes';
 import { getUserCookieName, setCookieWithDomain } from './cookieHelpers';
 import {
@@ -205,7 +209,7 @@ export const IFrameHelper = {
 
     postback(data) {
       dispatchWindowEvent({
-        eventName: 'chatwoot:postback',
+        eventName: CHATWOOT_POSTBACK,
         data,
       });
     },