A quick google reveals a number of plug-ins for jQuery, including this one
The Package Control plug-in will probably help you to install a jQuery plug-in. Otherwise, you could create a folder named 'jQuery' (in your 'Packages' folder) and copy a number of files/snippets to it.
The jQuery snippets/completions will probably display for any .js file, but I suppose if you're using jQuery you're likely to be using it most of the time anyway
"I'm here to save your life. But if I'm going to do that, I'll need total uninanonynymity." Me Myself & Irene.