A couple of thoughts/questions re GeoJson

[akariv]

Many thanks for this highly useful effort. A couple of thoughts/questions that could be converted to tickets from my side:

• GeoJSON is a subset of / extends JSON support, but by having to explicitly initialise it (rather than load as a separate module, let's say) it seems to be treated on par. Would we do the same for TSV? SQLite? GeoPackage? But I guess it's too early to worry about scalability when there are only 3 formats supported at this time.
• On this note, the introduction of default_serializer to file_formats.py might warrant it's own PR, or at least a check through the other code and documentation.
• What about auto-detecting a GeoJSON file?
• We should link to RFC 7946 or similar. To me this effort is also closely related to the effort to create a Geo Data Package. Currently the README doesn't really cover file format support, but it should.
• We might want to stick to a .geojson file extension in the example, though make it clear that this is not required.
• Where does validation happen? I.e. where would you hand off to a more specialized library like python-geojson.
• What about streaming support, e.g. would dataflows handle use cases similar to https://github.com/4xle/geojson-vt-stream ?
• It would be very helpful to add a section to the Tutorial

Originally posted by @loleg in #153 (comment)