dep: bump github-markdown-css from 5.8.1 to 5.9.0

Bumps [github-markdown-css](https://github.com/sindresorhus/github-markdown-css) from 5.8.1 to 5.9.0.
- [Release notes](https://github.com/sindresorhus/github-markdown-css/releases)
- [Commits](sindresorhus/github-markdown-css@v5.8.1...v5.9.0)

---
updated-dependencies:
- dependency-name: github-markdown-css
  dependency-version: 5.9.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

package-lock.json

@@ -57,7 +57,7 @@
     "@fortawesome/fontawesome-free": "^7.2.0",
     "@tailwindcss/postcss": "^4.1.18",
     "autoprefixer": "^10.4.24",
-    "github-markdown-css": "^5.8.1",
+    "github-markdown-css": "^5.9.0",
     "gulp": "^5.0.1",
     "gulp-concat": "^2.6.1",
     "gulp-dart-sass": "^1.1.0",