Add support for platform osx-arm64

[pya]

Modern machines with MacOs come with M[1-5] processors, i.e. the platform is osx-arm64. I added osx-arm64 to tool.pixi.workspace.platforms. The package proj was missing. I added it with Pixi. All tests for the environments py311, py312, py313, and dev run my MacBook Pro M1 Max. The tasks build, install, and lint run as well.

[wpbonelli]

thanks @pya! I'm on M2 so should have had this by now :)

[wpbonelli]

looks like hdf5 is missing on mac. any idea whether it's better to get that thru homebrew or conda? conda for consistency?

[pya]

I always go with conda-forge. I really try to avoid homebrew. It broke my system all too often.

[wpbonelli]

well, I guess the right way to do this is to add pixi config to pyproject.toml as described here, but that is a bit verbose and I'd like to try it separately first. so to get this PR in I will just install hdf5 with brew in CI for now.

[wpbonelli]

@pya do you mind either allowing maintainers to push to your PRs or adding a step to the test CI job before the "Setup pixi" step like

   - name: Install HDF5
     if: runner.os == 'macOS'
     run: brew install hdf5

[pya]

@wpbonelli I couldn't find the button that allows pushing to PRs. So I added the task to CI.

[wpbonelli]

thanks @pya the pixi env shifted underfoot so I'll just merge and then update it separately. appreciate your doing this. any other feedback you have on all this is very welcome though please be aware it is early stage and we are still mostly in a "make it work" mindset, in design terms we are aiming to "make it right" immediately, but expect implementation to be rough for some time