Update source code link in index.html

Author: Cat-Ling

assets/templates/index.html

@@ -24,7 +24,7 @@ <h1 class="logo">Flinternet</h1>
 
     <footer class="container" style="margin-top: auto; padding: 4rem 1rem;">
         <div class="footer-links">
-            <a href="https://github.com/flinternet/flinternet" target="_blank">Source code</a>
+            <a href="https://github.com/cat-ling/binternet-go" target="_blank">Source code</a>
             <a href="/legal">Legal notice</a>
         </div>
         <div class="footer-copy" style="margin-top: 1rem; color: var(--text-dim); font-size: 0.8rem;">