Document online `Setup.hs haddock --for-hackage`

[mpilgrem]

About 10 years ago, Cabal added the --for-hackage flag:

• https://github.com/haskell/cabal/pull/2852/files

This pull request seeks to document it online.

In order to do so, it also documents the undocumented --html, --contents-location=url, and --quickjump flags, based on their in-app documentation and that for similar documented fields.

• [x] Patches conform to the coding conventions.
• [x] Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions). N/A