Update README.md

Author: arunk140

README.md

@@ -77,6 +77,6 @@ zip gnome-command-menu.zip icon.svg metadata.json extension.js README.md LICENSE
 ```
 git clone https://github.com/arunk140/gnome-command-menu.git
 cd gnome-command-menu
-gnome-extensions package 
+gnome-extensions pack
 gnome-extensions install command-menu@arunk140.com.shell-extension.zip
 ```