CI should detect when breaking changes are introduced

[nyurik]

Note that this uses a separate semver job - which may be an overkill - perhaps it should be added to the clippy job? I wouldn't want it to compile so many times in different VMs unless needed.

See https://github.com/obi1kenobi/cargo-semver-checks?tab=readme-ov-file#quick-start

[KodrAus]

Thanks for the PR @nyurik! This seems like something worth doing going forwards. Would you be happy to port this to using cargo-semver-checks directly with cargo install rather than through the cargo-semver-checks-action GitHub action? That way we have a clearer idea of what each job is doing and what actions we're depending on. The tool itself looks good to me 🙂