We don't have documentation on how to create a social plugin. However, JFBConnect comes with multiple social plugins that can be modified in a pretty straightforward way if the provider uses OAuth2.
There is mainly one section where you specify the OAuth2 URLs. JFBConnect takes care of most of the other work to authenticate the user using that system. For data like profile import, that's unique to each social network's API, but also abstracted quite a bit into our plugins.
I hope that helps give you a starting point, but if you start developing and have any questions, just let us know.