On Wayland, add support for fractional scaling

This adds support for the fractional scaling on Wayland via the
wp-fractional-scale protocol.

Co-authored-by: Julian Orth <ju.orth@gmail.com>

src/platform_impl/linux/wayland/mod.rs

@@ -10,6 +10,7 @@ pub use window::Window;
 mod env;
 mod event_loop;
 mod output;
+mod protocols;
 mod seat;
 mod window;