Feature request: Add layer to represent geojson

[IgnacioHR]

Hello there,

I'm using flutter_osm_plugin in my app but now I've the requirement to draw features coming from geojson. I can't find documentation or examples about how to do it.

Reading the documentation of flutter_map_geojson it looks like I could do it if I migrate my code to flutter_map.

I'm adding this issue just to document the requirement on flutter_osm_plugin for consideration in the roadmap