Updated free-courses-en.md > Added Three.js subcategory + course (#9008)

* Updated free-courses-en.md

Added Three.js subcategory and course.

* adjusted the spacing

* Update courses/free-courses-en.md

Adjustment done.

Co-authored-by: Eric Hellman <eric@hellman.net>

Co-authored-by: Eric Hellman <eric@hellman.net>

courses/free-courses-en.md

@@ -55,6 +55,7 @@
     * [React Native](#react-native)
     * [Redux](#redux)
     * [Svelte](#svelte)
+    * [Three.js](#threejs)
     * [Vue.js](#vuejs)
 * [Julia](#julia)   
 * [Kotlin](#kotlin)
@@ -877,6 +878,11 @@
 * [Svelte Tutorial](https://www.youtube.com/watch?v=vhGiGqZ78Rs) - Beau Carnes, freeCodeCamp (YouTube)
 
 
+#### Three.js
+
+* [Three.js Tutorial Crash Course](https://www.youtube.com/watch?v=YK1Sw_hnm58) - Chris Courses
+
+
 #### Vue.js
 
 * [Full Stack Vue.js, Express & MongoDB](https://www.youtube.com/playlist?list=PLillGF-RfqbYSx-Ab1xWVanGKtowTsnNm) - Traversy Media (YouTube)