To do for psql to show installable extensions

I'd like to propose a wiki to-do item for a backslash command in psql which would show all installable extensions, basically just a wrapper around 'select * from pg_available_extensions'.

I've wanted it a few times recently, mostly in testing.

Any reason this wouldn't be desirable?  What should it be called? I thought of \dx+, but the + is already used to show the objects associated with the extensions.  (Althought it seems like it would more in keeping with other usage if \dx+ only listed the objects if it was given a pattern, and did what I propose if given no pattern)

Cheers,

Jeff