chore: replace deprecated eslint markdown plugin (#6646)

## 📄 Description

Replaces the deprecated `eslint-plugin-markdown` with
`@eslint/markdown`.

Author: gfellerph

packages/documentation/package.json

@@ -38,6 +38,7 @@
   },
   "devDependencies": {
     "@eslint/js": "9.18.0",
+    "@eslint/markdown": "7.5.1",
     "@kurbar/storybook-addon-docs-stencil": "8.0.0",
     "@lit/task": "1.0.3",
     "@open-wc/lit-helpers": "0.7.0",
@@ -57,7 +58,6 @@
     "cypress-axe": "1.6.0",
     "eslint": "9.18.0",
     "eslint-plugin-cypress": "4.2.0",
-    "eslint-plugin-markdown": "5.1.0",
     "eslint-plugin-mdx": "3.1.5",
     "eslint-plugin-react": "7.37.5",
     "eslint-plugin-storybook": "9.0.10",