build(deps-dev): bump gatsby-source-filesystem from 3.0.0 to 3.1.0 (#533

)

Bumps [gatsby-source-filesystem](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-source-filesystem) from 3.0.0 to 3.1.0.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-source-filesystem/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-source-filesystem@3.1.0/packages/gatsby-source-filesystem)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -76,7 +76,7 @@
     "gatsby-plugin-react-helmet": "4.1.0",
     "gatsby-plugin-react-svg": "3.0.0",
     "gatsby-plugin-sass": "4.1.0",
-    "gatsby-source-filesystem": "3.0.0",
+    "gatsby-source-filesystem": "3.1.0",
     "gatsby-transformer-react-docgen": "6.1.0",
     "glob": "7.1.6",
     "html-loader": "2.1.2",