Fugue integration

[alxmrs]

Support Fugue Dataframes. Test execution on PySpark, Dask, DuckDB, and BQ via Fugue.

[alxmrs]

Solves some of the same goals as #4.

[alxmrs]

I am unsure if fugue or another library is the best choice. E.g. consider ibis: https://ibis-project.org/why

[alxmrs]

Further, I don't know if fugue will help move data from xarray to distributed execution engines or not. For several interesting integrations, like BQ, it looks like fugue just reads from there, it does not load data into the system.

More knowledge about their df interface is needed.

[alxmrs]

I think ibis or Beam is a better choice than fugue. There isn't a need to integrate within this package. Closing.