Add CI check to ensure mozjs is bumped

[jschwe]

For purposes of publishing to crates.io, we should also bump the mozjs version number, and update the dependency on mozjs-sys. cargo will give an error, if we update the mozjs-sys version in mozjs-sys/Cargo.toml, but forget to update the dependency in mozjs/Cargo.toml since we depend on an exact version by using the = specifier.
The only thing we need to check in CI is that the mozjs version is also bumped, since that would prevent publishing to crates.io (without further changes).

[sagudev]

Should we also request bump for any changes in mozjs? Or maybe is this planed as part of other PRs.

[jschwe]

Should we also request bump for any changes in mozjs? Or maybe is this planed as part of other PRs.

Tbh, I did not consider that yet. I guess we would want a release for every change, since the repos are tightly coupled, so it would make sense to require that.

[sagudev]

Hm, actually it is safe to not bump mozjs version for any change (but we need this for mozjs-sys because of artifacts), so maybe we do not need this PR? I can see how it could be useful (to not forget bump if one wants to use this in servo), but also not if we want to land multiple PRs (in short span of time) and not release version for each one (I am worried we will spam to many version - and our crates are big).

[jschwe]

Okay, I can make a seperate PR for the mozjs detection, and we can discuss that there. Removed the changes from here again.
Edit: Although I think that just mozjs itself would be quite a small crate.