Load map.js explicitly from canvas.html.

Without this it's hard to get to map.js in the debug tools since Chrome
doesn't know about the anonymous js. Probably improves logging too.

resources/ui/map/canvas.html

@@ -24,6 +24,7 @@
         integrity="sha384-XAr1poM2RCR9/QQFki7ylrGSdmvYE0NuHghuRuxb/k9zJQA53y6qR5te5jJRZlcL"
         crossorigin="">
     </script>
+    <script src="map.js" defer="defer"></script>
     <style>
         body { padding: 0; margin: 0; }
         html, body, #map { height: 100%; }