ci(release.yml): add crates publishing job

[vdice]

• Adds a step to publish the spin-sdk crate on each v* release tag

Depends on #2151

TODO:

• Open Question: What to do re: publishing the spin-macro crate, a dependency of the spin-sdk crate?
  • Keep spin-macro crate version separate from workspace/spin-sdk version (Currently it is 0.1.0)
    • Manually publish crate when this version is bumped, manually create PR to update crate version in spin-sdk's Cargo.toml
    • Add automation to publish crate when this version is bumped (could be slightly tricky if not associated with a git tag), potentially also add automation to create a PR to spin-sdk's Cargo.toml to rev the version
  • Align spin-macro crate version with workspace version (i.e. release tag version) and publish prior to publishing spin-sdk (Haven't tested this, will the approach work via back-to-back jobs in a GH workflow?)

[dicej]

Given that spin-macro changes about as often as spin-sdk, we might as well give them the same version and publish them at the same time.