Thread Chapters 2.2.2

• Fix "declaration of ...::addAnalysisHooks(AnalyzerHooks $hooks) must be compatible..." error.

• Fix error when no sub-context is provided.
• Import functions.

• Support for XenForo 2.3.0+.
• Bump minimum PHP version to 8.0+.
• Code cleanup.

• Fix an issue preventing thread chapters from working on pinned first posts.

• Harden template modifications and compatibility tweaks for XF 2.2.

• Add an editor icon to the chapter BB code.
• Bump minimum XF version requirement to 2.1.5.