ci: enforce PR titles to follow the conventional commit specification

[thomaseizinger]

Description

As per decision in #3083, we want to use the conventional commits in our repository. To make sure this actually happens, this patch adds a workflow that validates PR titles to follow this convention. Together with our mergify configuration, these PR titles end up being the commit message title when squash-merging a pull request.

Related: #3083
Related: libp2p/github-mgmt#93

Notes

I've copied the workflow from libp2p/github-mgmt#93. Once this is merged, we will have to add this as a required check there as well. We could do that in an atomic manner by adding the workflow via the mgmt repository. Although that makes iteration slightly more annoying.

I'd suggest we add the workflow here first and once we are happy with the configuration and see it working, we enforce its presence (and it passing) via https://github.com/libp2p/github-mgmt.

Links to any relevant issues

Open Questions

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• A changelog entry has been made in the appropriate crates

[mxinden]

🙏

[thomaseizinger]

What do we think about also limiting the length of the PR title to 72 such that we follow common Git guidelines?

[mxinden]

Works for me @thomaseizinger.

[thomaseizinger]

Here is the PR for it: #3267