Sign Windows release

[dabreegster]

Everybody on Windows gets the "developer unverified" security warning, because the binary isn't signed. Looks like this might not actually be so hard to fix with Github Actions. First step is to buy a code signing cert.

• https://github.com/marketplace/actions/code-sign-a-file-with-pfx-certificate
• https://github.com/jonfriesen/windows-signer-action (older, less maintained?)

Other references (including for Mac, which I can try next):

• https://shipshape.io/blog/signing-electron-apps-with-github-actions/
• GitHub Actions workflow to build and sign macOS binary executables simonw/datasette#1171

[dabreegster]

https://old.reddit.com/r/rust/comments/112hcvp/how_can_i_codesign_executables_for_different/

[dabreegster]

https://github.com/gyroflow/gyroflow/blob/master/_scripts/windows.just