[Feature Request] Port GNOME extension to KWin Effect

[wheaney]

KWin supports scripted effects that are backed by GLSL fragment shader, and the ability to set uniform variables for the shader:

• The original PR that got merged to include such effects
• The ScriptedEffect implementation

Questions still remain:

• Can an effect be applied to a whole monitor view?
• Can run for long periods? not just short-lived visual effects
• Can we stream uniform variable updates to it continuously?

We'll also want to make sure it can have a dconf integration to watch settings that come from the Breezy Desktop app. I've seen mentions of keyboard shortcuts, so I think it'll be able to handle that.