Bump @storybook/addon-mdx-gfm from 8.6.15 to 8.6.18

Bumps [@storybook/addon-mdx-gfm](https://github.com/storybookjs/storybook/tree/HEAD/code/addons/gfm) from 8.6.15 to 8.6.18.
- [Release notes](https://github.com/storybookjs/storybook/releases)
- [Changelog](https://github.com/storybookjs/storybook/blob/v8.6.18/CHANGELOG.md)
- [Commits](https://github.com/storybookjs/storybook/commits/v8.6.18/code/addons/gfm)

---
updated-dependencies:
- dependency-name: "@storybook/addon-mdx-gfm"
  dependency-version: 8.6.18
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package-lock.json

@@ -90,7 +90,7 @@
     "@storybook/addon-docs": "8.6.15",
     "@storybook/addon-essentials": "8.6.15",
     "@storybook/addon-links": "8.6.15",
-    "@storybook/addon-mdx-gfm": "8.6.15",
+    "@storybook/addon-mdx-gfm": "8.6.18",
     "@storybook/addon-webpack5-compiler-swc": "^3.0.0",
     "@storybook/html": "8.6.15",
     "@storybook/html-webpack5": "8.6.15",