Documentation stanza for libraries with mlds

Context

The stanza was removed when switching to manifest, probably lost in a rebase.

This MR:

• adds support for mld doc in the manifest
• documents its use as part of the mld effort
• uses the new features for the libraries that need it

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, the Development Version section of CHANGES.md for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR