Improve CI workflow for github actions

[CJLove]

Nice to haves:

• MacOS build matrix for multiple clang versions
• Windows build matrix for VS2019 and 2022
• Exercise unit tests on Windows (sort out DLL locations)

[detective-sokka]

Hi @CJLove I would love to work on this issue.

[CJLove]

@detective-sokka - thanks for the offer! Feel free to take a shot at this and submit a PR.