Feature request: links.jf2 filter by wm-property

[tantek]

A links.jf2 endpoint request could be improved with a wm-property filter, e.g. to only retrieve "rsvp" or "like-of" or perhaps a comma delimited list of values e.g. "like-of,repost-of,in-reply-to".

Use cases, similar to those documented in #82 (but this is a much simpler feature request)

• retrieving only rsvps: ?wm-property=rsvp
• retrieving only comments, reposts, likes: ?wm-property=like-of,repost-of,in-reply-to

Only existing values that are returned in wm-property in the jf2 result are valid for the wm-property query param