ckubs you might have to interact with Flarum's post javascript component to get such library working correctly. This might require developer knowledge. That's because Flarum is a single page app and most of these "plugins" are made for "static" html pages.
There's very little skeleton required for extensions, it all depends on what part you want to extend. You should have a look at existing extensions to see how it's done.
As Flarum is still beta, creating an extension can require some digging in the source code. Might be a good opportunity if you're actually trying to learn web development. Or if you're not into that, there are developers around here who might be able to help.
But do try datitisev suggestion first, I might well be too pessimistic and maybe that library does work that way without any additional effort ?
On a different side, what does that library actually do ? Does it interact with YouTube links ? YouTube iframes ? Don't Flarum existing extensions cover that ? There could be a risk it completely breaks the post rendering or extensions like MediaEmbed if not properly integrated with Flarum ?
