Add GeoJSON serialization to Area object

[perliedman]

I noticed the Area object has wkb and wkt methods, but lacks the geojson method.

I guess this is because the geojson methods in Node and Way are implemented on the node-osmium side rather than relying on libosmium's GeoJSON serialization; with the current API, the same thing is not possible to do for areas.

I've hacked up a fix that uses libosmium's GeoJSONFactory to serialize an Area, and then parses the resulting string using JSON.parse. It feels a bit iffy, but seems to do the job.

Since this is my first dive into node-osmium/libosmium, I totally expect there to be better ways to do this. Any pointers on alternatives or improvements would be great!

[joto]

You are right, your solution is a bit "iffy". I found a better one and just committed it. There is now a geojson() function on the Area object, too.

[perliedman]

Thanks, your fix does indeed look much cleaner!