Add link to “Building a Custom React Renderer”

Add link to Sophie Alpert’s talk on  “Building a Custom React Renderer”

README.md

@@ -169,6 +169,7 @@
 * [**JavaScript**: _How to write your own Virtual DOM_](https://medium.com/@deathmood/how-to-write-your-own-virtual-dom-ee74acc13060)
 * [**JavaScript**: _Building a frontend framework, from scratch, with components (templating, state, VDOM)_](https://mfrachet.github.io/create-frontend-framework/)
 * [**JavaScript**: _Build your own React_](https://pomb.us/build-your-own-react/)
+* [**JavaScript**: _Building a Custom React Renderer_](https://youtu.be/CGpMlWVcHok)
 
 #### Build your own `Game`