Configuration documentation

[roidelapluie]

We need some documentation about Prometheus configuration.

Something like we have in the reference docs but with only the most useful fields, and with examples. It should be prometheus-version agnostic. Features introduced recently should be marked as such.

[hdost]

docs-ng project potentially?

[roidelapluie]

Yes definitively

[LeviHarrison]

Either as a part of this or as a compliment, I think some more relabeling configuration examples would be nice.

Adding on to this I don't believe we even have a comprehensive list of labels you can use in relabeling currently, (eg. __address__, job, __metrics_path__ ...)