Update 502 pages and associated static assets

Summary:
Bump 502 pages to 751c1c6b40e5

• 751c1c6b40e5 Add 502 page for phabricator.wolfplex.be

Bump assets.dereckson.be to 250f8ed57e94

• 250f8ed57e94 Add Œil-de-nuit estampes

Stage assets.wolfplex.org

• 799c4a2f11086 Serve CSS and JS resources for Matrix message design
• fe9f5be8a5dd0 Publish homepage to describe domain purpose
• f59df5b7ba106 Initialize repository

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1965