Widget Opacity

[soundprojects]

Is your feature request related to a problem? Please describe.
It seems that is currently not possible to easily set the opacity of a widget

Describe the solution you'd like
Would be nice if we can set the opacity with a set_opacity() method

Describe alternatives you've considered
Tried using colours to match background colours or use the alpha parameter in the premultiplied function but this is a bit tedious if you just want to change the opacity for a set of elements

Additional context

[emilk]

Can I ask what you want widget transparency for?

[soundprojects]

Of course. A widget opacity option would allow me to create fade transitions more easily using the egui_animations crate.

I use a workaround currently where I animate an overlay the size of my widget with the same color as the background color but this does not scale well.