Add build for osx-arm64?

[scottyhq]

Comment:

I'm not familiar with the build process for osx-arm64 but just wanted to link to this issue for supporting multi-architecture pangeo docker images:
pangeo-data/pangeo-docker-images#396 (comment)

[ocefpaf]

I added conda-forge/conda-forge-pinning-feedstock#6066 to start the process but I'm curious if people are really using ciso or if that is just a left over in the image package list.

I am the maintainer of ciso BTW and I have to confess I'm keeping it alive just b/c I did not try python-stratify yet. Also, many packages that are target for specific models, like mit gcm, probably have that functionality already.

[ocefpaf]

Done in #30