Discussion: folder structure when using modules that require javascript/css/images?

Traditionally, before modules came around, I used to have this folder structure as my standard for any app:

- shinyapp/
|- ui.R
|- server.R
|- www/
|---- js/
|---- css/
|---- img/

And all was good.

Now with the increased use of modules, I often have a modules/ folder as well, where the code for different modules live. But one thing that I haven't quite found a convention for is what to do when each module has its own CSS/JS/images. Where would you place these files?