Include Required Dependencies Of Rollup In "dependencies"

[chadhietala]

This fixes 2 issues:

1. This ensures that required dependencies of rollup are downloaded on a consumers machine. Right now I think things may be accidentally working.
2. Fixes the following issue where TypeScript consumers were receiving type errors due to missing type definitions for acorn.

[lukastaegert]

Even though these dependencies might be required for some of the internal TypeScript types to be working correctly, they are by no means necessary for rollup to work because they are already part of the rollup bundle. The question should be rather how to make the types work without those dependencies that users of rollup do not come into contact with anyway.

[lukastaegert]

I guess since no better suggestion has been made yet, this will go into the next feature release.