Adding cargo semver checks

[seattlelizzard]

Adding cargo semver checks to Github actions yaml

[BenLeadbetter]

Thanks for the PR! 🏅

[BenLeadbetter]

This patch would have cargo semver checks running on each PR against develop. This would be redundant since the check only makes sense to run on releases - PRs against develop do not tend to involve a cargo version bump, which would make the semver checks useless, if I understand correctly.

One thing we could do is have the checks run only for PRs against main (since these tend to be the release PRs)

[BenLeadbetter]

BTW, I'm currently working on some automatic release start / finish actions which would also automatically run the checks, but these are still WIP.