Bump gatsby-plugin-sitemap from 2.9.0 to 2.11.0

Bumps [gatsby-plugin-sitemap](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-sitemap) from 2.9.0 to 2.11.0.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-sitemap/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-plugin-sitemap@2.11.0/packages/gatsby-plugin-sitemap)

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

Author: dependabot[bot]

package.json

@@ -8,7 +8,7 @@
     "@mdx-js/mdx": "^1.6.21",
     "@mdx-js/react": "^1.6.21",
     "@tailwindcss/typography": "^0.3.1",
-    "gatsby": "^2.27.4",
+    "gatsby": "^2.31.0",
     "gatsby-image": "^2.6.0",
     "gatsby-plugin-feed": "^2.8.0",
     "gatsby-plugin-feed-mdx": "^1.0.1",
@@ -18,7 +18,7 @@
     "gatsby-plugin-offline": "^3.5.0",
     "gatsby-plugin-react-helmet": "^3.5.0",
     "gatsby-plugin-sharp": "^2.9.1",
-    "gatsby-plugin-sitemap": "^2.9.0",
+    "gatsby-plugin-sitemap": "^2.11.0",
     "gatsby-plugin-typography": "^2.7.0",
     "gatsby-remark-copy-linked-files": "^2.5.0",
     "gatsby-remark-images": "^3.6.0",