FR: add a backdrop setting like lazy.nvim

[chrisgrieser]

Is your feature request related to a problem? Please describe.
Not really a problem, just a suggestion for a nice aesthetic addition.

Describe the solution you'd like
lazy.nvim recently introduced a backdrop setting, which I think would also be a good fit for dressing.nvim. Basically, when a float is created, the background becomes de-emphasized:

The respective code implementation seems to be around here

Describe alternatives you've considered
There are some plugins that attempt something similar, however, they were all buggy for me – lazy.nvim has the first implementation appears to work bugfree

[julian-meaningfulgigs]

Bumping this. Also saw it in Lazy, would love to see it ported here.

[jamestrew]

There are some plugins that attempt something similar, however, they were all buggy for me

This is because doing this sort of stuff is all really jank involving creating dummy windows with winblend and using tons of autocommands.
With one window like lazy's dashboard thing, it's probably fairly manageable but I have some reservations about adding this to telescope.

I'm also a little unsure if it's on individual plugins to support this sort of background dimming and if we're all to adopt it just because lazy did it.

That said, if someone wants to have a go at implementing it, I'll be open to considering it then though. It may not be that hard. I would look at mount and unmount methods on Layout (off the top of my head on my phone, sorry if I'm wrong).