Wait.. How do we figure out what files to include in index.handlebars?
The MapQuest documentation at https://developer.mapquest.com/documentation/mapquest-js/v1.3/ tells us about these files.
Where do we get this code from?
Again, the MapQuest documentation at https://developer.mapquest.com/documentation/mapquest-js/v1.3/ informs us about how to use the MapQuest API for developement. The above link tells us about how to create a map. We can find the documentation for adding markers to map here: https://leafletjs.com/reference-1.3.0.html#marker