[META] document all operator-framework object annotations per project

[estroz]

This idea recently came up, and I figured the api repo is the best place to document org-wide annotations. There really should be some authoritative list of these annotations, which are currently (maybe) documented by the projects that use them, ex. the set of Operator SDK plugin names, helm-operator annotations, etc.

Suggested structure: docs/annotations/<repo or project or component>.md with a list of each annotation and description:

- key: operatorframework.io/paused
  key-format: <optional string for formatted keys, an alternative to "key">
  values: ["true", "True"]
  value-format: <optional string for formatted values, an alternative to "values">
  owner: https://github.com/operator-framework/operator-lib <!-- some owner link -->
  refs: ["predicate", "handler"] <!-- list of subpackages, files, etc -->
  description: |
	A long-form description of the annotation. Should be fairly all-encompassing if set.
  description-link: <optional link to a description, an alternative to "description">

/kind documentation /priority important-longterm