Feat: Background only in transparent mode

[AlexvZyl]

When enabling transparent mode, we should provide an option where only the background is transparent, and other floating windows and components are opaque.

[5-pebbles]

Well I just test implemented this:

            transparent = {
                bg = false,
                float = true,
            },

& I think that's probably the best way of doing it.

[5-pebbles]

I actually kind of like it with just transparent floating windows...

but it works the other way around: