Add YT mirror

Author: max-arnold

docs/source/development.md

@@ -5,7 +5,7 @@
 
 ## Video tutorial
 
-A short video tutorial on how to build a custom firmware version:
+A short video tutorial on how to build a custom firmware version ([YouTube mirror](https://youtu.be/WrPj2_DdfjI)):
 
 <iframe width="720" height="405" src="https://rutube.ru/play/embed/1ff6fc7246260b3d404acebd0435d785?p=faQjyf7QWhT3bff2GDrReQ" frameBorder="0" allow="clipboard-write; autoplay" webkitAllowFullScreen mozallowfullscreen allowFullScreen></iframe>