release 0.1.0

[keewis]

Since the last dev release almost a year ago, a lot has changed in the library:

• grid info objects to allow non-conforming metadata, and as a layer to contain all the API weirdness of the implementing libraries
• replace the assign_* methods with property methods (inspired by xarray's .dt and .str accessors)
• lots of tests!
• the computation of cell boundaries
• most recently, the visualization using lonboard

This is definitely enough for a release! However, to be useful we really need some documentation, which I think has to be done before the release (API documentation plus one tutorial for each DGGS should be sufficient for now). For the tutorials, I think we want to resolve #71 first.

I think this is the items needed :

• renaming the primary grid parameter from resolution to level #64 (breaking change, should be done now where there's not as many users affected)
• tutorial datasets #71: expose example datasets through xdggs.tutorial #84 and xdggs-data
• documentation #76
• allow overriding the grid using a dict or a GridInfo object #56 (punted to a later release)