MediaWiki namespace banners

When the extension is installed, these appear at the top of pages in the Help:Namespace

• Top-notice-ns-1
• Top-notice-ns-101
• Top-notice-ns-11
• Top-notice-ns-13
• Top-notice-ns-15
• Top-notice-ns-3
• Top-notice-ns-5
• Top-notice-ns-6
• Top-notice-ns-7
• Top-notice-ns-9