New callout support in Apex

Callouts just got a lot more flexible in the latest release of Apex. I now support Quarto, Pandoc, Obsidian/Bear, and Python Markdown flavors of callouts. Obsidian and Bear style still works The original blockquote-style syntax is still first-class: > [!NOTE] Heads up > This is a note. That still renders to Apex callout HTML with type-aware classes and optional collapsible behavior using + and - .…