Add documentation for annotations and config strings, including release versions

[xtaje]

Describe the change you'd like to see

Add documentation for annotations and configmap strings, including their release versions. Changes to string formats should also be documented as part of release notes.

Additional context The PRs below change the annotations strings used for autoscaling (e.g. minScale -> min-scale, min-scale -> scale-min), or the configmaps (camel case -> kebab-case).

These changes are currently not documented anywhere, which makes it hard to determine when something has changed, or the effect an upgrade might have. Also some people might not be able to upgrade to the latest versions of knative. When a string is misspelled, there is no warning or way to detect it.

https://github.com/knative/serving/pull/12329 https://github.com/knative/serving/issues/12932 https://github.com/knative/serving/pull/12071/files