Add GH repo link

app/pages/index.html

@@ -3,3 +3,5 @@ <h1 class="font-bold text3 mb2 text-center">Enhance Image!</h1>
 <size-reporter></size-reporter>
 
 <p class="text-center mb2 text-1">When starting from a narrow viewport and resizing wider, the current image source will change to accommodate larger viewports. Starting from a wide viewport and resizing narrower, the current image source will not be updated, to avoid needless network requests.</p>
+
+<p class="text-center mb2 text-1"><a class="underline" href="https://github.com/enhance-dev/enhance-example-image">View source on GitHub</a></p>