Index only scans wiki page

https://wiki.postgresql.org/wiki/Index-only_scans

This page is seriously out of date.  It suggests they are not yet
implemented, but only being talked about.

Would someone who knows a lot about the subject (which is why I'm
sending this hackers, not web)  like to take a whack at updating this?
 Otherwise, I'd like to just replace the whole page with a discussion
of the limitations and trade-offs involved in using them as they
currently exist

Thanks,

Jeff