gnu: Add gnome-shell-extension-transparent-window.

* gnu/packages/gnome-xyz.scm
(gnome-shell-extension-transparent-window): New variable.

Signed-off-by: Liliana Marie Prikler <liliana.prikler@gmail.com>

gnu/packages/gnome-xyz.scm

@@ -1051,6 +1051,37 @@ in the status menu below the volume slider.  Various active ports like HDMI,
 Speakers etc. of the same device are also displayed for selection.")
     (license license:gpl3+)))
 
+(define-public gnome-shell-extension-transparent-window
+  (let ((commit "cc9bc70c192dd565fa6f1d1b28d9a20f99684f2a")
+        (revision "45"))
+    (package
+      (name "gnome-shell-extension-transparent-window")
+      (version (git-version "0" revision commit))
+      (source
+       (origin
+         (method git-fetch)
+         (uri (git-reference
+               (url (string-append "https://github.com/pbxqdown/"
+                                   "gnome-shell-extension-transparent-window"))
+               (commit commit)))
+         (file-name (git-file-name name version))
+         (sha256
+          (base32
+           "1f9iqqjpmmylqz0ws8cy5rs475bwzi7jy44q9ip44ig2acz2wxzp"))))
+      (build-system copy-build-system)
+      (arguments
+       (list
+        #:install-plan
+        #~'(("."
+             #$(string-append "/share/gnome-shell/extensions"
+                              "/transparent-window@pbxqdown.github.com")))))
+      (home-page
+       "https://github.com/pbxqdown/gnome-shell-extension-transparent-window")
+      (synopsis "Change the opacity of windows in GNOME Shell")
+      (description "This extension adds keybindings to change the opacity
+of windows.")
+      (license license:expat))))
+
 (define-public arc-theme
   (package
     (name "arc-theme")