Add github repository link to demo app

Author: AXeL-dev

projects/demo/src/app/app.component.html

@@ -1,7 +1,7 @@
 <nz-layout class="layout">
   <nz-header>
     <div class="logo">ngx-diff2html Demo</div>
-    <a class="github-icon float-right" href="#">
+    <a class="github-icon float-right" href="https://github.com/AXeL-dev/ngx-diff2html">
       <i nz-icon nzType="github" nzTheme="outline"></i>
     </a>
   </nz-header>