Add git-hook for commit message conformance

Personally, I care more about the format of the Git commit messages.

This is because when I am hacking on Toolbox, especially when I am debugging existing code and trying to figure out why some things are done the way they are, I am not looking at the Git history through GitHub's web UI. The web UI is quite limiting in the Git commands that it exposes. I am mainly using Git's command line interface, because it's right next to my text editor.

For me, the GitHub issue or pull request carry extra secondary context. They are where people discuss the commits, the different trade-offs and they add extra secondary context to the changes that landed. So, *sometimes*, if the commit message isn't enough, then I end up reading through the issue or pull request to understand the different view points, pros & cons, who said what, etc..

In other words, the Git commits are *primary*, and the GitHub issues and pull requests are *secondary*.

So, I wish we could have some Git hooks that would ensure that:
* Commit messages don't exceed 72 characters per line.
* Commit messages contain a link to an issue, if there's one, or the GitHub pull request.
* Prevent trailing white spaces.

... because I think sometimes, whether for valid or invalid reasons, contributors will override the GitHub templates, which is fine, but I don't want them to play fast and loose with the actual Git commits.

_Originally posted by @debarshiray in https://github.com/containers/toolbox/issues/932#issuecomment-976485333_