Add ARM support for GitHub actions

[bee-san]

https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/accessing-contextual-information-about-workflow-runs#runner-context

We should add arm support to our github actions.

here's one comment about it:

 FYI, I did start looking at this:

1. adding the appropriate build to the matrix and setting cross: true works perfectly!
2. …but then the Python tests fail for that step only.
3. it looks like actions-rs/toolchain is now deprecated and equally, it's not clear what the de facto standard Action might be.

So the build isn't too tricky but getting it working in a pipeline is proving a little more rabbit-hole-y than expected.

Originally posted by @PsypherPunk in #579 (comment)