Update 12.4-shared-drawing-canvas.md

This is a whiteboard application made using:
>p5js ⭐ 
>node 
>socket.io ⚡ 
>lazyBrush 🖌️ 
>and my brain :P

Demo Link : https://pwhiteboard.herokuapp.com

Author: weirdomind

_Tutorials/12-websockets/12.4-shared-drawing-canvas.md

@@ -29,6 +29,12 @@ contributions:
       name: "Bohdan Drahan"
       url: "https://github.com/bohdandrahan"
     url: "https://github.com/bohdandrahan/Shared-Canvas"
+  - title: "pWhiteboard"
+    author:
+      name: "Mind0Bender"
+      url: https://github.com/Mind0Bender
+    url: https://pwhiteboard.herokuapp.com
+    source: https://github.com/Mind0Bender/pwhiteboard
 ---
 
 This video puts all of the pieces together: node, express, p5.js, and socket.io to show how to program a shared, collaborative drawing canvas.