Add notes to refer to docs when modifying the JS files

resources/js/maps/index.js

@@ -1,7 +1,11 @@
 /**
- * All of the functionality required for maps
+ * Before you edit these, read the documentation on how these files are compiled:
+ * https://docs.phpvms.net/customize/building-assets
+ *
+ * Edits here don't take place until you compile these assets and then upload them.
  */
 
+
 import render_airspace_map from './airspace_map';
 import render_live_map from './live_map';
 import render_route_map from './route_map';