[Janitorial] Please add MAINTAINERS.md

[RichiH]

I'm going through all of prometheus-community/ and adding an issue to create a MAINTAINERS.md where it's missing.

Ideally model it on https://github.com/prometheus/prometheus/blob/main/MAINTAINERS.md with a split between general mantainers and subsystem maintainers if applicable.

Thanks, Richard

[slrtbtfs]

Hi,

I’m technically the Maintainer of this project, but there has been significant bitrot over the last years and I while i had plans to get things going again i didn’t actually get around to do that.

So the current state is that it’s practically unmaintained but i would be happy to help if someone is interested in getting things working again.

[slrtbtfs]

Linking to https://github.com/prometheus-community/promql-langserver/issues/269 because these projects are mutually dependent on each other.