Check into docs configuration to have docs in separate repo

[valadas]

See documentation here https://www.npmjs.com/package/gh-pages

The idea is that if the module is in a private repository, publishing its documentation in that repository may be less than useful as we don't get a free public website to host those docs. But if I am reading the docs correctly, we could publish the docs to any other repository (for github-pages purposes of having free hosting).

When testing this, we need to also consider the implications of someone submitting a PR to fix some typo on the docs repository instead of the private code repository.