[kube-prometheus-stack]docs: add a FAQ

[davhdavh]

What this PR does / why we need it

Add a FAQ, because this helm is severely lacking in a bit of help for common setups and issues.

Checklist

• DCO signed
• [-] Chart Version bumped
• Title of the PR starts with chart name (e.g. [prometheus-couchdb-exporter])

[GMartinez-Sisti]

I like the concept, but I think we should add this to another file -> FAQ.md, and link it from the main README since that file is already huge.

[davhdavh]

It wont show up on e.g. artifacthub if it isn't in the readme.
Besides, the current readme file is way way under-documented and is mostly just the same list of CRD fixes 10 times.

[GMartinez-Sisti]

It wont show up on e.g. artifacthub if it isn't in the readme. Besides, the current readme file is way way under-documented and is mostly just the same list of CRD fixes 10 times.

IMHO an FAQ is not something you need on the main README, the README file should contain only information about the chart, how to deploy and how to upgrade, everything else can be on other files. With this change the README ends up with 1321 lines, and if you go all the way to the end we already have some topics that would fit an FAQ, e.g. Work-Arounds for Known Issues, Migrating from stable/prometheus-operator chart and Redeploy with new name (downtime), to name a few. I would be happy to send these to the new FAQ file and just add a link.

However note that I don't oppose adding the FAQ to the README, if you feel that brings value, at least we could create a table of contents for the main topics and add it on top of the README file to make it a little easier to understand. This is a good example: https://github.com/runatlantis/helm-charts/tree/main/charts/atlantis#links. WDYT?