add github link to header

website/index.html

@@ -35,6 +35,7 @@
 				<div class="nav-collapse collapse">
 					<ul class="nav">
 						<li><a class="nav-item" href="index.html">Home</a></li>
+						<li><a class="nav-item" href="https://github.com/Microsoft/monaco-editor">GitHub</a></li>
 						<li><a class="nav-item" href="playground.html">Playground</a></li>
 						<li><a class="nav-item" href="monarch.html">Monarch</a></li>
 						<li><a class="nav-item" href="https://www.npmjs.com/package/monaco-editor">Download</a></li>