Updated Add a Custom Service (markdown)

Add-a-Custom-Service.md

@@ -7,7 +7,7 @@
 5. Enter a URL for the Logo of the service to display it in the tab.
 6. In Advanced option, there is an _Unread Code_ field. This field you will use it if the service you are adding is not notifying an activity (new messages, new emails, etc) throw the title of the page (Ex. "(2) Facebook Messenger"). The number 2 means there are 2 messages unread. This code will be injected to the service page to run it (must return an Integer) and it will be embeded into this code:
 
-```
+```javascript
 function checkUnread() {
     updateBadge(_YOUR_CODE_WILL_BE_PLACED_HERE_);
 }