Add MDViewer to the Markdown tool directory

_tools/mdviewer.md

@@ -0,0 +1,90 @@
+---
+title: MDViewer
+category: documents
+description: "MDViewer is a native macOS Markdown viewer with inline editing, Git history, Mermaid diagrams, and syntax highlighting."
+icon: mdviewer.png
+website: https://getmd.ma
+syntax:
+  - id: headings
+    available: y
+  - id: paragraphs
+    available: y
+  - id: line-breaks
+    available: y
+  - id: bold
+    available: y
+  - id: italic
+    available: y
+  - id: blockquotes
+    available: y
+  - id: ordered-lists
+    available: y
+  - id: unordered-lists
+    available: y
+  - id: code
+    available: y
+  - id: horizontal-rules
+    available: y
+  - id: links
+    available: y
+  - id: images
+    available: y
+  - id: tables
+    available: y
+  - id: fenced-code-blocks
+    available: y
+  - id: syntax-highlighting
+    available: y
+    notes: "Supports [over 180 programming languages](https://getmd.ma/guides/syntax-highlighting-in-markdown)."
+  - id: footnotes
+    available: y
+  - id: heading-ids
+    available: y
+    notes: "Automatically generated. Used for the smart table of contents sidebar."
+  - id: definition-lists
+    available: n
+  - id: strikethrough
+    available: y
+  - id: task-lists
+    available: y
+  - id: emoji-cp
+    available: y
+  - id: emoji-sc
+    available: y
+  - id: highlight
+    available: n
+  - id: subscript
+    available: n
+  - id: superscript
+    available: n
+  - id: auto-url-linking
+    available: y
+  - id: disabling-auto-url
+    available: y
+  - id: html
+    available: y
+see-also:
+  - name: MDViewer guides
+    link: https://getmd.ma/guides/
+---
+
+MDViewer is a fast, native macOS application for reading and editing Markdown files. Built with SwiftUI — not Electron — it opens instantly from Finder and works as your default `.md` app.
+
+### Features
+
+- **Inline editing** — edit Markdown in place and save with ⌘S, no separate editor needed.
+- **Git history and diffs** — browse file history and see color-coded changes without leaving the app.
+- **Mermaid diagrams** — renders flowcharts, sequence diagrams, ER diagrams, and Gantt charts as interactive SVGs.
+- **KaTeX math** — renders LaTeX math formulas inline and in display blocks.
+- **Smart table of contents** — auto-generated sidebar navigation from headings.
+- **QuickLook** — preview `.md`, `.json`, and `.mermaid` files with Space in Finder.
+- **JSON viewer** — collapsible tree view for JSON files.
+- **Tabbed interface** — open multiple files in one window.
+- **Dark mode** — full support, follows system preference.
+- **PDF export** — convert Markdown to styled PDF documents.
+
+MDViewer requires macOS 13 Ventura or later and runs natively on both Apple Silicon and Intel Macs. It is free during early access.
+
+{% include tool-syntax-table.html %}
+
+{% include see-also.html %}