Add xdg-utils and wsl-open

Add `xdg-utils` to add functions like `xdg-open` to run commands such
as `mob timer open` and have them open a browser.

Also add `wsl-open` so this works within WSL.

lib/shared/home-manager-packages.nix

@@ -50,6 +50,7 @@ with pkgs;
   virtualenv
   wget
   xcp
+  xdg-utils
   xh
   yarn
 ]