This doesn't handle deletions of the files

[onnimonni]

The plugin should keep up records of everything that was installed. This way we could clean up earlier files during update and delete them when they are deleted by composer.

Hook delete function into pre-update-package and pre-delete-package.

[sybbear]

This feature would be really handy.
How complex is this to implement?

[onnimonni]

Not that complex, I think this will be an easy task to implement.

I'm happy to apply a pull request if you want to finish this feature.