[charter] list Document Policy as a deliverable

[samuelweiler]

@dontcallmedom suggests that we list Document Policy as a deliverable.

@dveditz @mikewest, opinions?

[annevk]

As noted in WICG/document-policy#26 I have concerns about the name as I think we also want this for workers.

cc @clelland @jan-ivar

[clelland]

We navigated Feature -> Permissions Policy while the spec was under this group's charter, so I don't know if naming discussions should necessarily block this.
(I'm very supportive of having those discussions, and having them early. FWIW)

[samuelweiler]

Having seen little discussion here, I'm opting for the "no changes" approach. It seems clear that this is in scope and can be adopted later.