Create release workflow

[mattdowdell]

Tag workflow:

1. Trigger on-demand
2. Run tests + build artifacts for Windows, Linux, MacOS (compress + checksum)
3. Create tag based on the version in Cargo.toml.
4. Create draft release, e.g. Version X.Y.Z.
5. Attach builds + checksums to release.

Publish workflow:

1. Trigger on release create/publish/released (unsure which is appropriate)
2. Publish to crates.io