Build, test and release artifacts for Windows

[brianmcgee]

Is your feature request related to a problem? Please describe.

With Buildbot, we build and test on x86_64-linux, aarch64-linux, and aarch64-darwin by default. Goreleaser is currently configured to produce artefacts for linux and darwin. We can start producing binaries for Windows easily enough, but they won't be tested, and I suspect there might be some path-related shenanigans afoot.

Describe the solution you'd like

Before we add the Windows artefacts, I would like a Github workflow that builds and tests everything.

One obstacle will be the cli/format_test, which requires all the formatters listed in nix/packages/treefmt/formatters.nix to be installed. I don't know how difficult this will be on Windows.

I haven't used Windows in years, and it will take time for me to set up a local dev VM and be able to test things locally myself.