Add docs about native histograms.

[bwplotka]

cc @beorn7

EDIT: Practices and Guide/Tutorial on how to enable them e2e from Go client, through Prometheus to querying

[beorn7]

I would imagine we should update https://prometheus.io/docs/practices/histograms/ for native histograms, and then add a Guide or a Tutorial with the hands-on help. (What's actually the difference between Guides and Tutorials on prometheus.io?)

But first of all, I have to write a proper spec (or a candidate spec) in the Concepts section.

A blog post is maybe the wrong format (beyond an "announcements and highlights" thing).

[bwplotka]

Nice, Guide/Tutorial and Practices sounds good! Changing the title.

[bwplotka]

No idea what's the Guide vs Tutorial. To me it feels Guides are general rough steps you should do, whereas Tutorial feel like reproducible scenario you could walk in with more detailed commands (?)