docs: add mdformat-ruff to integrations.md (#9924)

Can [mdformat-ruff](https://github.com/Freed-Wu/mdformat-ruff) be hosted
in <https://github.com/astral-sh> like other integrations of ruff? TIA!

docs/integrations.md

@@ -353,6 +353,12 @@ Alternatively, it can be used via the [Apheleia](https://github.com/radian-softw
 Ruff is also available via the [`textmate2-ruff-linter`](https://github.com/vigo/textmate2-ruff-linter)
 bundle for TextMate.
 
+## mdformat (Unofficial)
+
+[mdformat](https://mdformat.readthedocs.io/en/stable/users/plugins.html#code-formatter-plugins) is
+capable of formatting code blocks within Markdown. The [`mdformat-ruff`](https://github.com/Freed-Wu/mdformat-ruff)
+plugin enables mdformat to format Python code blocks with Ruff.
+
 ## GitHub Actions
 
 GitHub Actions has everything you need to run Ruff out-of-the-box: