This was originally done to make the gitignoring easier, but ended up
being somewhat more complex when trying to include files, so they're
moving out closer to the point of use.
Most of this was stolen from prior work:
6c4c2aa9ae
The one thing that took me an unreasonably long time to figure out was
that SVGs without width/height don't work (correctly? at all?) in
OpenLayers. Possibly due to this issue?:
https://github.com/openlayers/openlayers/issues/14196
Anyway, it was fixed by adding a width and height attribute to the pin
SVG.
