How to include javascript node_modules dependencies in Rails Engine?

I'm working on fork of simple_discussion gem which is Rails Engine to extend the functionality of forum in the parent Rails application.

I'm adding Markdown support using SimpleMDE. I've thought of one way to include it's minified js as assets in assets/javascripts/ folder so that this js will attached to its parent application.

Try creating a new JavaScript file in the assets/javascripts/ directory of your Rails app then copy the contents of the SimpleMDE JavaScript file into this new file.