Add cookie banner

docs/_includes/global/cupcake.html

@@ -0,0 +1,12 @@
+<script src="{{ site.url }}/assets/vendor/cupcakes-3.1.0.min.js"></script>
+
+<script>
+  window.addEventListener("load", function(){
+  window.cupcakeconsent.initialise({
+    "content": {
+      "message": "Just so you know, this website uses cookies.",
+      "dismiss": "<span>👍</span> Got it!",
+      "link": "What are cookies?"
+    }
+  })});
+</script>