Update index.html

index.html

@@ -74,7 +74,7 @@ <h2>Generating graphs</h2>
 
       <h2>Contributing</h2>
       <p><strong>threatdown</strong> is an open standard inviting anyone to help develop, extend, and improve it.</p>
-      <p><a href="">Join us on GitHub</a>.</p>
+      <p><a href="https://github.com/threatdown/threatdown-graph">Join us on GitHub</a>.</p>
 
     </main>
     <aside id="what-is-threat-modeling">
@@ -100,4 +100,4 @@ <h2>Threat models should be secured</h2>
       <a class="logo" href="https://code4rena.com">maintained by <img alt="Code4rena" src="https://raw.githubusercontent.com/code-423n4/media-kit/main/code4rena-logo.png"></a>
     </footer>
   </body>
-</html>
+</html>