Not quite the same functionality but on that page you can click the drop-down on the search bar and "Add GitHub". Then the github command line is one of the options for search providers alongside Google, Wikipedia etc. If you select it as the default, you can Ctrl-K up to the search bar and type a command without leaving the keyboard.

Also (and I'm not sure how useful this is) you can select some text, right-click it and execute it as a GitHub command.