More GeoInterface methods

[asinghvi17]

This PR adds the following features:

• Add more methods for Rect construction, since that's basically used as our bbox type. Calling Rect on any geometry should now return a Rect which is the bbox of that geometry.
• Implement GeoInterface.extent on top of the previous Rect changes.
• Implement GeometryBasics.geointerface_geomtype, which GeoInterface picks up to allow other packages' geometries to be easily converted to GeometryBasics geometries (TODO: should we use this behaviour in Makie somehow?)
• Implement a lot of polygon operations like centroid, distance, signed area, etc. Also define GeoInterface methods backing these.
• Reformat and add small optimizations to src/geointerface.jl.

TODOs still remaining:

• Add a method to find distance which works well everywhere (the current method only checks for distance to nearest vertex)
• Look through the whole package, find more methods which GeoInterface methods can call
• Add tests
• Make sure that performance is good! (tested with Polylabel.jl, it was pretty fast).

[rafaqz]

Can we break this up into smaller PRs so it gets merged sooner?

Specifically can we add a PR for geointerface_geomtypes just so convert(GeometryBasices, geom) works?

[asinghvi17]

A lot of this has been taken over by GeometryOps!

[SimonDanisch]

So we can close this?