x11/swaylock-plugin: add new port
This is a fork of swaylock, a screen locking utility for Wayland
compositors. With swaylock-plugin, you can for your lockscreen
background display the animated output from any wallpaper program that
implements the wlr-layer-shell-unstable-v1 protocol. All you have to
do is run "swaylock-plugin --command 'my-wallpaper ...'", where
"my-wallpaper ..." is replaced by your desired program. Examples:
- swaybg, which displays regular background images
- mpvpaper, which lets you play videos
- shaderbg, renders OpenGL shaders
- rwalkbg, a very slow animation
- wscreensaver, an experiment in porting a few xscreensaver hacks to Wayland