Add an option to force capitalizing the subject line

This convention is well-known in the community and deemed a good practice in several articles related to Git commit messages, ex. https://cbea.ms/git-commit/#capitalize.

However, it’s currently not possible to get it configured, due to Python stock regex module re limitations - we can’t have a regex pattern that matches a Unicode uppercase character.

There’re 2 possible approaches to this:

• Implement this as a rule and maybe a default one.

• Switch to regex module, which has richer regex support with full backward compatibility with the re module.

[sigmavirus24]

I don’t think this must be done with regular expressions but it would be good to add even if it’s off by default

[jorisroovers]

Bump @novadev94 😃