feat(close) Add promotional close page

interface_config.js

 
     // A html text to be shown to guests on the close page, false disables it
     CLOSE_PAGE_GUEST_HINT: false,
+    SHOW_PROMOTIONAL_CLOSE_PAGE: false,
     RANDOM_AVATAR_URL_PREFIX: false,
     RANDOM_AVATAR_URL_SUFFIX: false,
     FILM_STRIP_MAX_HEIGHT: 120,

react/features/app/actions.js

 import logger from './logger';
 
 declare var APP: Object;
+declare var interfaceConfig: Object;
+
 
 /**
  * Triggers an in-app navigation to a specific route. Allows navigation to be
             // fine but pointless to include it because contextRoot is the current
             // directory.
             newPathname.startsWith('./')
-            && (newPathname = newPathname.substring(2));
+                && (newPathname = newPathname.substring(2));
             newPathname = getLocationContextRoot(windowLocation) + newPathname;
         }
 
         windowLocation.replace(locationURL.toString());
 
         if (window.self !== window.top
-                && locationURL.search === oldSearchString) {
+            && locationURL.search === oldSearchString) {
             // NOTE: Assuming that only the hash or search part of the URL will
             // be changed!
             // location.reload will not trigger redirect/reload for iframe when
             // to close page
             window.sessionStorage.setItem('guest', isGuest);
 
-            dispatch(redirectToStaticPage(`static/${
-                options.feedbackSubmitted ? 'close.html' : 'close2.html'}`));
+            let path = 'close.html';
+
+            if (interfaceConfig.SHOW_PROMOTIONAL_CLOSE_PAGE) {
+                path = 'close3.html';
+            } else if (!options.feedbackSubmitted) {
+                path = 'close2.html';
+            }
+
+            dispatch(redirectToStaticPage(`static/${path}`));
 
             return;
         }
         }
     };
 }
-