rosenthal: wayland-for-hyprland: Export variable.

As reported in <https://github.com/rakino/Rosenthal/issues/15> , the
inconsistency between wayland versions may cause issue on hyprland.

This commit exports ‘wayland-for-hyprland’, a newer version of "wayland"
package used by hyprland in rosenthal, so that affected users can install it
as a workaround.

* rosenthal/packages/wm.scm (wayland-for-hyprland): Export variable.

rosenthal/packages/wm.scm

@@ -39,7 +39,8 @@
   #:use-module (gnu packages wm)
   #:use-module (gnu packages xdisorg)
   #:use-module (gnu packages xml)
-  #:use-module (gnu packages xorg))
+  #:use-module (gnu packages xorg)
+  #:export (wayland-for-hyprland))
 
 (define libinput-minimal-for-hyprland
   (package