Moves video from header

This was causing issues in word press

Author: jkelroy

gitkraken-client/themes.md

@@ -5,10 +5,11 @@ description: Using and creating themes in GitKraken Client.
 taxonomy:
     category: gitkraken-client
 
+---
+
 <div class='embed-container embed-container--16-9'>
     <iframe width="560" height="315" src="https://www.youtube.com/embed/_TMprlLc740?ecver=1" frameborder="0" allowfullscreen></iframe>
 </div>
----
 
 ## Built-in Themes