Add PromQL language support

[arendjr]

This PR adds support for PromQL: https://prometheus.io/docs/prometheus/latest/querying/examples/

[RunDevelopment]

Thank you for the PR @arendjr!

I gave your PR a quick look and left you some comments. I'll give it a more in-depth review later.

Additional notes:

• We only use single-quoted strings
• Please quote all token names (e.g. 'comment', 'range-duration', etc) (like here).
• Please use an IIFE to fix global namespace pollution (like here).

[arendjr]

Thanks for the thorough feedback already! I have addressed the styling issues, split keywords and functions as appropriate, simplified some things and added another comment to address one of your questions :) To be honest, I'm not sure about all the original motivations, as I reused some code from the Monaco highlighter and the blog post I referenced, but thanks to your review, I think it's pretty cleaned up now.

[RunDevelopment]

Thank you for the quick response!

I still have some minor nits but it's overall it looks really good now.

[RunDevelopment]

Please rebuild, so I can merge.

[arendjr]

Done!

[RunDevelopment]

Thank you for contributing @arendjr!

[arendjr]

Thanks for your support! 🚀