Bump gatsby-transformer-remark from 6.12.3 to 6.13.1

Bumps [gatsby-transformer-remark](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-transformer-remark) from 6.12.3 to 6.13.1.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-transformer-remark/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-transformer-remark)

---
updated-dependencies:
- dependency-name: gatsby-transformer-remark
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

gatsby-theme-doctocat-typescript/package.json

@@ -52,7 +52,7 @@
     "gatsby-plugin-styled-components": "^6.12.0",
     "gatsby-remark-images": "^7.12.3",
     "gatsby-source-filesystem": "^5.12.1",
-    "gatsby-transformer-remark": "^6.12.3",
+    "gatsby-transformer-remark": "^6.13.1",
     "gatsby-transformer-sharp": "^5.12.3",
     "gatsby-transformer-yaml": "^5.12.0",
     "get-pkg-repo": "^5.0.0",