Add youtube video

Author: master-q

index.html

@@ -64,7 +64,8 @@ <h3>
 
 <h3>
 <a name="demovideo" class="anchor" href="#demovideo"><span class="octicon octicon-link"></span></a>Demo video</h3>
-<iframe width="420" height="315" src="//www.youtube.com/embed/5uPue0Jo1nc" frameborder="0" allowfullscreen></iframe>
+<iframe width="338" height="253" src="https://www.youtube.com/embed/5uPue0Jo1nc" frameborder="0" allowfullscreen></iframe>
+<iframe width="451" height="253" src="https://www.youtube.com/embed/_Sx6GzuTm9k" frameborder="0" allowfullscreen></iframe>
 
 <h3>
 <a name="lang" class="anchor" href="#lang"><span class="octicon octicon-link"></span></a>What language will challenge?</h3>