Support for other map frameworks

[eyeseast]

I like Mapbox, but it's nice to have other options.

Actions are adaptors. A package like ulysses.leaflet or ulysses.google would just need to implement standard actions that expect a leaflet.Map or google.Map object, instead of Mapbox GL. It's just a contract.

The core actions are: flyTo, fitBounds, noop. And maybe showAll if we can figure that one out.

[eyeseast]

I'm assuming maplibre will work as a drop-in replacement for Mapbox, if needed.