What we actually needs is a web standard list (via API) that provides the shortcuts and the search URL like so (as an example):

  !gh { https://github.com/search&q=$QUERY$ }
  !ebay { http://www.ebay.co.uk/sch/i.html?&_nkw=$QUERY$ }

Then all browsers (and other apps) could provide these standard shortcuts in their search functions.