notifications: Improve HTML/CSS for desktop notifications.

static/js/notifications.js

@@ -222,6 +222,7 @@ function in_browser_notify(message, title, content, raw_operators, opts) {
         gravatar_url: ui.small_avatar_url(message),
         title: title,
         content: content,
+        message_id: message.id,
     }));
 
     $('.top-right').notify({

static/styles/zulip.css

@@ -2273,6 +2273,10 @@ button.topic_edit_cancel {
     text-align: center;
 }
 
+.notification {
+    cursor: pointer;
+}
+
 #empty_narrow_private_message p,
 #empty_narrow_message p {
     text-align: center;

static/templates/notification.handlebars

@@ -1,5 +1,5 @@
 {{! Content of in-browser notifications }}
-<div>
+<div class="notification" data-message-id="{{message_id}}">
     <div class="notifications-gravatar">
         <img src="{{gravatar_url}}" />
     </div>