fix(deps): bump gatsby-source-filesystem from 5.11.0 to 5.12.0

Bumps [gatsby-source-filesystem](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-source-filesystem) from 5.11.0 to 5.12.0.
- [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@5.12.0/packages/gatsby-source-filesystem)

---
updated-dependencies:
- dependency-name: gatsby-source-filesystem
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

package.json

@@ -26,7 +26,7 @@
     "gatsby-remark-copy-linked-files": "^6.12.0",
     "gatsby-remark-images": "^7.12.0",
     "gatsby-remark-relative-images": "^2.0.5",
-    "gatsby-source-filesystem": "^5.11.0",
+    "gatsby-source-filesystem": "^5.12.0",
     "gatsby-transformer-remark": "^6.12.0",
     "gatsby-transformer-sharp": "^5.12.0",
     "gatsby-transformer-yaml": "^5.12.0",