docs: reorganize documentation directory structure

[ovidiutirla]

What this PR does / why we need it:
Fixes #1903

How does this change affect the cardinality of KSM: (increases, decreases or does not change cardinality)
no impact

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes ##1903

Testing

$ make doccheck 
GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -ldflags "-s -w -X github.com/prometheus/common/version.Version=v2.11.0 -X github.com/prometheus/common/version.Revision=fc204cb8 -X github.com/prometheus/common/version.Branch=reorg-docs -X github.com/prometheus/common/[email protected] -X github.com/prometheus/common/version.BuildDate=2024-04-03T10:30:58Z" -o kube-state-metrics
gomplate -d config=./data.yaml --file README.md.tpl > README.md
>> generating docs
embedmd -w `find . -path ./vendor -prune -o -name "*.md" -print`
git diff --no-ext-diff --quiet --exit-code README.md
- Checking if the generated documentation is up to date...
- Checking if the documentation is in sync with the code...
OK
- Checking for orphan documentation files
OK

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[ovidiutirla]

adding @dgrisonnet. Happy to address any additional feedback.

[CatherineF-dev]

overall lgtm. Added few comments.

[ovidiutirla]

hey @rexagod, I'm happy to address any other feedback. Thank you.

[dgrisonnet]

/assign @rexagod

[dgrisonnet]

/triage accepted

[rexagod]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ovidiutirla, rexagod

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