Add video for CDN

pages/watch.js

@@ -37,6 +37,12 @@ const WatchList = () => (
     <div className='pt-5 pb-5 bg-light border-top'>
       <div className='container'>
         <div className='row'>
+          <RowBlock
+            openExternal
+            title={'Content Delivery Networks'}
+            subtitle="Learn what the CDNs are, how they work and why you might use them."
+            url='https://www.youtube.com/watch?v=6DXEPcXKQNY'
+          />
           <RowBlock
             openExternal
             title={'Load Balancers 101'}