Bump gatsby from 2.19.18 to 2.19.28

Bumps [gatsby](https://github.com/gatsbyjs/gatsby) from 2.19.18 to 2.19.28.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/compare/[email protected]@2.19.28)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

packages/www/package.json

@@ -10,7 +10,7 @@
     "copy-text-to-clipboard": "^2.1.1",
     "eslint-mdx": "^1.6.8",
     "eslint-plugin-mdx": "^1.6.8",
-    "gatsby": "^2.19.18",
+    "gatsby": "^2.19.28",
     "gatsby-image": "^2.2.42",
     "gatsby-plugin-eslint": "^2.0.8",
     "gatsby-plugin-manifest": "^2.2.42",