Update README.md

Fix links to spritesheet testing tool.

README.md

@@ -74,8 +74,9 @@ See the examples below:
 
 If you want to quickly test your spritesheets in a 2D game, here's a simple "sandbox" game/tool where you can upload the raw spritesheet outputs and spawn in your characters to move around:
 
-Link: https://svntax.github.io/pixel-art-spritesheet-sandbox/
-Source: https://github.com/svntax/pixel-art-spritesheet-sandbox
+Link to tool [here](https://svntax.github.io/pixel-art-spritesheet-sandbox/)
+
+Source code [here](https://github.com/svntax/pixel-art-spritesheet-sandbox)
 
 ## Notes