Build fixes and improvements

[h0tw1r3]

• Fix building gem on Windows (all compilers)
• Replace travis workflow with github action workflow to test building on windows, linux, and mac
• Add release workflow to publish native gems for mac and windows

[h0tw1r3]

Release workflow requires setting up a RUBYGEMS_OIDC_API_ROLE secret.
See https://github.com/rubygems/configure-rubygems-credentials for more details

[mfazekas]

@h0tw1r3 thanks much, looks great!

On gem publishing is it possible to enforce MFA, so GitHub actions you'd have to enter the OTP to publish a new release?

[h0tw1r3]

@mfazekas separated the release workflow out into #23 as it's a separate thing I think.

[mfazekas]

@h0tw1r3 thanks much!