GeoJSON type conflicts with the GeoJSON package

[rafaqz]

What do you think @evetion? GeoJSONstring ? It would be breaking but probably a good time to break things.

[evetion]

I'd also consider not exporting these? The same will eventually happen to KML, GML, WKB etc. Might be good to think about how to document this for other package developers as well, these are just unparsed, wrapped formats to dispatch on.

If we export, maybe something like GeoJSONFormat?