Add Inkstone to the tools directory

[xyc]

Hi Matt,

This adds Inkstone, a macOS Markdown editor that works directly on plain .md files in any folder, to the tools directory. I'm its developer.

• Website: https://inkstone.md
• Markdown processor: Milkdown's CommonMark and GFM presets (remark / micromark), plus remark-math, remark-wiki-link and remark-frontmatter
• Price: paid ($29.99 one-time), free 14-day trial; macOS 14+

Files:

• _tools/inkstone.md, following the existing tool pages (category documents, same syntax IDs and order as Typora)
• assets/images/tool-icons/inkstone.png (256×256 app icon)
• assets/images/tools/inkstone.png (editor screenshot)

The syntax table comes from the editor's parser and serializer configuration. I've marked the gaps as n rather than leaving them out: custom heading IDs, definition lists, emoji shortcodes, highlight, subscript and superscript. HTML is p, since only comments, img and video are rendered.

Happy to adjust anything.

🤖 Generated with Claude Code