Serve saas-mediawiki development version

Summary:
This repository responsibility is to serve the different wiki configuration.

Ref T845.

Test Plan: require "/var/51-wwwroot/saas-mediawiki/LocalSettings.php";

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T845

Differential Revision: https://devcentral.nasqueron.org/D1440