API reference is out of sync with NPM package

[pvditto]

Users who look for the library's documentation will come across the rendered docs linked from this repo at https://getditto.github.io/react-ditto/. However, these docs reflect the state of the master branch, which currently is out of sync with the latest published release.

Possible solutions could be:

• only publishing documentation when also publishing an NPM release (probably easiest to implement)
• publishing documentation for releases to named subdirectories, e.g. https://getditto.github.io/react-ditto/v11.0 and redirecting from the GH docs root to the latest version's page. (nice because older docs versions are kept online)