more apparent focus by opacity or a stroke

[Stooovie]

Hi, MacOS has relatively low visual differentiation of focused window. It would be great if Amethyst could either lower opacity or contrast of unfocused windows, OR draw a thin stroke/border around focused window. Possible?

[ianyh]

There is a long-standing request that is being tracked here: #127

My general thought is that it's super reasonable in theory, but I'm not sure how best to implement it in practice.