Deploy Scribunto extensions for MediaWiki SaaS

Summary:
Scribunto could benefit of several other extensions,
as explained at https://www.mediawiki.org/wiki/Extension:Scribunto

Ref T845.

Test Plan: salt-call --local state.apply roles/saas-mediawiki/mediawiki

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T845

Differential Revision: https://devcentral.nasqueron.org/D1450