signing: signpath

[davidkna]

Support signing on WIndows via signpath alongside the other options.

Signpath offers free code signing for some open-source projects, as of recently GHA is supported. Sample workflow using signpath for signing on GHA. Successful signing also requires setting up an appropriate artifact configuration because uploads via GHA are zipped.

• Documentation for use with Appveyor: https://about.signpath.io/documentation/trusted-build-systems/appveyor
• Documentation for use with GHA: https://about.signpath.io/documentation/trusted-build-systems/github

[ashleygwilliams]

hey @davidkna ! thanks for filing and sorry for the delay in response. i think we would be open to mentoring and accepting a PR for this integration if you were interested in working on it. we're in the midst of wrapping up a config migration, so we are a bit low bandwidth in the near term.