Service for hosting native JavaScript ES modules
Have you considered CDNjs.com:


It supports CORS headers, it is dedicated to JavaScript after all.
It supports HTTP/2 as well as SPDY.
The cache duration is 355 days, which is probably plenty long enough.
Cloudflare is used as the CDN, they provide it to cdnjs.org for free.


Adding your library is a bit more than a one-liner unfortunately as you need to submit a pull request to their GitHub repository.  You will also need to have a certain popularity requirement:


  For the new library request issue, please make sure it's not a personal project, we have a basic requirement for the popularity, like 200 stars on GitHub or 800 downloads/month on npm registry.