use docker to publish the website
use docker to publish the website

Summary:
It's too much of a pain to maintain a local Ruby and Jekyll
installation, so use Docker to rebuild the website.

Reviewed By: genevievehelsel

Differential Revision: D37356695

fbshipit-source-id: fa521f2543d982d348c767ffed8ec6db207a5d53

facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman