How can I load jQuery (and more generally, libraries) into my Safari app extension?

Hi @bweinstein if you're reading this 🙂. I'm having a lot of trouble sourcing libraries (specificaly jQuery) into my app extension. I described my issue in greater detail in this StackOverflow post:

xcode - Unable to import JQuery library into my Safari app extension - Stack Overflow

I think an answer to this question would be valuable for other people on the forums because it's nowhere online and really empowers people to use all sorts of libraries, for another example Mousetrap (https://craig.is/killing/mice ). Thanks for the info at WWDC and thanks in-advance if you have time to answer this.