Add a config option to remove the TOC (Table of Contents)

[evanplaice]

Adding toc: 'none' to the config removes the TOC from the output.

This is useful for packages where the modules aren't all concatenated into one large file (ex ES Modules) and it's desirable to have the TOC centrally located somewhere else (ex the main README).

The implementation of this could be cleaner (ie rem noCategories and make TOC config an enum) but my focus was to modify the existing code as little as possible since this package doesn't appear to be actively maintained.