build(deps): bump gatsby from 3.0.4 to 3.1.0

Bumps [gatsby](https://github.com/gatsbyjs/gatsby) from 3.0.4 to 3.1.0.
- [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/gatsby@3.0.4...gatsby@3.1.0)

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

package.json

@@ -22,7 +22,7 @@
     "async.queue": "0.5.2",
     "babel-plugin-styled-components": "1.12.0",
     "classnames": "2.2.6",
-    "gatsby": "3.0.4",
+    "gatsby": "3.1.0",
     "gatsby-cli": "3.0.0",
     "gatsby-image": "3.0.0",
     "gatsby-plugin-canonical-urls": "3.0.0",