Added pixman and zigimg dependencies
Set up in build.zig, added to both exe and exe_check
Add new protocols:
river-layer-shell-v1
wlr-layer-shell-unstable-v1
xdg-shell (dep of wlr-layer-shell-unstable-v1)
Update Context.zig to hold wl_output, wl_shm, and a WallpaperImage
Also re-ordered all of its fields into alphabetical order
Context.create() now takes a Context.Options struct so that it takes
one arg instead of many smaller args.
Added new WallpaperImage.zig, but it's not yet actually used
