Update source code URL

Author: TheLastZombie

src/components/Legend.svelte

@@ -1,4 +1,4 @@
 <p class="mt-5">
   CSS optimizing happens directly in your browser using a browser-compatible build of clean-css. If you miss any functionality, you are more than welcome to 
-  <a href="https://github.com/jakubpawlowicz/clean-css/tree/master/docs" target="_blank">add it</a>!
-</p>
+  <a href="https://github.com/clean-css/clean-css.github.io" target="_blank">add it</a>!
+</p>