Add CTRL modifier for keyboard shortcut

As pointed out in RocketChat#12519 Chrome already uses `Shift+ESC`, colliding
with the 'mark all messages as read' keyboard shortcut in
RocketChat. This change adds the `CTRL` modifier to the shortcut,
i.e. mapping

     Shift+ESC | CTRL+ESC

packages/rocketchat-ui-master/client/main.js

@@ -24,7 +24,7 @@ Template.body.onRendered(function() {
 			toolbarSearch.focus(true);
 		}
 		const unread = Session.get('unread');
-		if (e.keyCode === 27 && e.shiftKey === true && (unread != null) && unread !== '') {
+		if (e.keyCode === 27 && (e.shiftKey === true || e.ctrlKey === true) && (unread != null) && unread !== '') {
 			e.preventDefault();
 			e.stopPropagation();
 			modal.open({