Transformation requirements

[asinghvi17]

In order to have a good transformation interface, we need to have some things (this was inspired by Cartopy):

1. Ways to get valid limits for arbitrary projections (cartopy has done this manually)

2. A better transformation interface which can handle the following things:

   • Resampling lines such that the correct curves appear.
   • Clipping/intersecting polygons such that they don't protrude out of the axes or have other transform-related problems (the old GeoMakie issue when plotting NaturalEarth land polygons)
   • Border-cutting lines, polygons, etc. so that we don't get lines which cross the map but shouldn't!

3. Classifications of projections as in Cartopy, e.g.

https://github.com/SciTools/cartopy/blob/e0b0d1f137ad91f91811638a1f573829e95300b6/lib/cartopy/mpl/gridliner.py#L25-L48

so we know what kind of grid line we have to draw (is the lat tick inside the gridline? Is it possible to provide labels at the border? If so how?)

4. Low-priority: projection and warping functions like so: https://scitools.org.uk/cartopy/docs/latest/reference/transformations.html (mainly the image warping utility as well as some other stuff). The image warping stuff can be done through ImageTransformations.jl.