Feature Request: would like dartdoc to provide doc'd/undoc'd stats + list of undoc'd elements

[csells]

Specifically, would like to be able to run dartdoc against a package, have it output how many elements are in the public API, how many of them do not have docs and output a list of those undoc'd elements.

[jcollins-g]

Switching to P2 as @csells has a workaround. This may be a project we work on during the summer internship season -- if so, we'll circle back around to try and make sure this meets those needs too.

[srawlins]

CC @jonasfj We'd love to steal yours 😁

[jonasfj]

This would also be nice for pub.dev, maybe we output a small metrics.json file or something.