Prepare Docker image for Pixelfed
This image is built on the top of the nginx/php7-fpm image,
battle-tested for Laravel applications with Auth Grove and
the notifications center.
Test Plan: Deploy container based on this image to Equatower.
Reviewed By: dereckson
Maniphest Tasks: T1481
Differential Revision: https://devcentral.nasqueron.org/D2023