Dependency management for web extensions

A file from one of my extensions has been copied, so that three of them now share a common code file. (It’s for accessing managed storage, with a fallback).

Keeping this updated to all extensions by copying is a bit tedious, as changes to one are not automatically applied to the other.

What is a clean way to use the same .js file in several web extensions?

Using AMD compatible module loader in Chrome Extension’s content script

I would like to use AMD modules in the content script of Chrome extensions and for that I need proper module loader/dependency manager. Since Chrome extension can load content scripts based on the rules placed in the manifest file, I was wondering is there a dependency manager that could just organise AMD based modules, similar to RequireJS but without the “loader” part.
I was aiming to use RequireJS for that, but all the solutions that I’ve found so far are a bit complicated and unnatural for use.