Option to temporarily override target room

[tripleee]

I like to occasionally use the cv-pls script to submit close requests to the Python room, but the userscript currently stores that as my default room for future close requests, too. I would like to be able to say "for this request only" when picking a room.

(I'm thinking a fairly simple solution would be to have a checkbox "make default" and not make the selected room the new default if that box is not checked, but I suppose other designs might make sense, too.)