Consider adding cargo-semver-checks to CI

[rustaceanrob]

Describe the enhancement
With the release of beta there seemed to be a strong preference to make nonbreaking patches.

Additional context

The CI job is:

- name: Check semver
  uses: obi1kenobi/cargo-semver-checks-action@v2

[storopoli]

You can assign to me.
We've implemented this in rust-bitcoin/rust-bitcoin#2946 and also pinned the version on CI in rust-bitcoin/rust-bitcoin@f76f682 with a cron CI job.

Or I can happily review a PR based on the stuff above as well.