Blurred background support

[christianparpart]

Support blurred background on all platforms.

• [ ] OS/X
• [x] Windows (Acrylic backdrop)
• [x] Linux: KDE window manager (kwin)
• [x] Linux: GNOME shell
• [ ] Linux: Wayland based KDE(/GNOME?)

Blur Topics

• https://learnopengl.com/Advanced-Lighting/Bloom

References:

• https://gist.github.com/ethanhs/0e157e4003812e99bf5bc7cb6f73459f
• https://github.com/riverar/sample-win32-acrylicblur/blob/master/MainWindow.xaml.cs
• https://stackoverflow.com/questions/44000217/mimicking-acrylic-in-a-win32-app

[Summertime]

• [ ] Linux: Gnome's Blur my Shell!

https://github.com/aunetx/blur-my-shell#application-blurring

[christianparpart]

• [ ] Linux: Gnome's Blur my Shell!

https://github.com/aunetx/blur-my-shell#application-blurring

Nice. Thanks!

[christianparpart]

@Summertime I've merged it to master, but we need to wait for https://github.com/aunetx/blur-my-shell/issues/300 to be addressed. That may not be instant, and you may need to just add contour's WM_CLASS to explicitly enable it until the referenced ticket is fixed, but it should hopefully only be a matter of time. And thx for the info on blur-my-shell ;-)