Can't get external JS library working: ImgCache is not defined

I’m trying to import and use the imgcache.js library. I’ve run this line:

npm install imgcache.js --save

I see it appears in packages.js, and it see it in the node_modules folder, but it does not get bundled into app.bundle.js when I build, so when I try to reference it, I get “ReferenceError: ImgCache is not defined”

I’ve used several other external libraries such as linq.js and accounting.js just by installing them from npm, so I’m not sure why this library is giving me grief.

I’ve forced it to work by adding a script tag in index.html and pointing to it, but I know this is not the right way to do it.

I see a few others have this same question, but there does not seem to be a resolution: Best practice to include external javascript libraries

Can anyone offer any suggestions? Thanks.