Specify that Scoop installation is for Windows (#1969)

To be consistent with other entries such as WinGet or Chocolatey

Author: yeikel

README.md

@@ -100,7 +100,7 @@ nix-env -iA nixos.lychee
 pkg install lychee
 ```
 
-### Scoop
+### Scoop (Windows)
 
 ```sh
 scoop install lychee