You can totally use JS libraries with Elm. Source: we do it all the time at NoRedInk, and we've been using Elm in production for our millions of users (as our go-to for all front-end work at the company, not just as a side thing) for the better part of a year now. :)
Details about our experience with Elm in production: https://www.youtube.com/watch?v=R2FtMbb-nLs