Undertale/Deltarune Wiki tweaks

This extension tweaks Undertale Wiki's and Deltarune Wiki's MediaWiki setup to our liking, to eliminate the need for patching MediaWiki core.

Tweaks

• Adds custom messages for custom user groups we introduced on the wikis
• Moves all notifications that were in the 'notices' section into the 'alert' section, as our skin only displays that section