Add support for "pint" Prometheus linter

[schmitmd]

Name: pint URL: https://github.com/cloudflare/pint

It's a linter for making sure your Prometheus rulesets aren't being inefficient or redundant.

This is totally a "nice-to-have" linter support request. Low-pri, the linter's not super complicated and I'm not in dire need of support, but I feel a sort of civic duty to submit it because, I mean, the project's name is "pint." It's like it's begging to be added to ALE.