Use wayland if available

This makes linux builds hybrid wayland/x11 instead of them being x11 only
with the slight downside of requiring wayland for building (not a problem for CI, and
I think the amount of people who are building from source on x11 only systems is small).

See this issue for more detail: fltk-rs/fltk-rs#1602

Cargo.toml

@@ -14,7 +14,7 @@ clap = { version = "4.5.18", features = ["derive"] }
 clap_complete = "4.5.29"
 dirs = "^5.0"
 fastwebsockets = { version = "0.8.0", features = ["upgrade", "unstable-split"] }
-fltk = { version = "^1" }
+fltk = { version = "^1.3", features = ["use-wayland"] }
 fltk-theme = "0.7.3"
 handlebars = "^6.1"
 http-body-util = "0.1.2"