Bump the gatsby group in /site with 9 updates (#218)

Bumps the gatsby group in /site with 9 updates:

| Package | From | To |
| --- | --- | --- |
| [gatsby](https://github.com/gatsbyjs/gatsby) | `5.12.11` | `5.13.3` |
| [gatsby-plugin-mdx](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-mdx) | `5.12.3` | `5.13.1` |
| [gatsby-plugin-react-helmet](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-react-helmet) | `6.12.0` | `6.13.1` |
| [gatsby-remark-autolink-headers](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-remark-autolink-headers) | `6.12.3` | `6.13.1` |
| [gatsby-remark-copy-linked-files](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-remark-copy-linked-files) | `6.12.0` | `6.13.1` |
| [gatsby-remark-prismjs](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-remark-prismjs) | `7.12.0` | `7.13.1` |
| [gatsby-remark-responsive-iframe](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-remark-responsive-iframe) | `6.12.0` | `6.13.1` |
| [gatsby-remark-smartypants](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-remark-smartypants) | `6.12.0` | `6.13.1` |
| [gatsby-transformer-sharp](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-transformer-sharp) | `5.12.3` | `5.13.1` |


Updates `gatsby` from 5.12.11 to 5.13.3
- [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]@5.13.3)

Updates `gatsby-plugin-mdx` from 5.12.3 to 5.13.1
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-mdx/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-plugin-mdx)

Updates `gatsby-plugin-react-helmet` from 6.12.0 to 6.13.1
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-react-helmet/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-plugin-react-helmet)

Updates `gatsby-remark-autolink-headers` 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-remark-autolink-headers/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-remark-autolink-headers)

Updates `gatsby-remark-copy-linked-files` from 6.12.0 to 6.13.1
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-remark-copy-linked-files/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-remark-copy-linked-files)

Updates `gatsby-remark-prismjs` from 7.12.0 to 7.13.1
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-remark-prismjs/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-remark-prismjs)

Updates `gatsby-remark-responsive-iframe` from 6.12.0 to 6.13.1
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-remark-responsive-iframe/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-remark-responsive-iframe)

Updates `gatsby-remark-smartypants` from 6.12.0 to 6.13.1
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-remark-smartypants/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-remark-smartypants)

Updates `gatsby-transformer-sharp` from 5.12.3 to 5.13.1
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-transformer-sharp/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-transformer-sharp)

---
updated-dependencies:
- dependency-name: gatsby
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: gatsby
- dependency-name: gatsby-plugin-mdx
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: gatsby
- dependency-name: gatsby-plugin-react-helmet
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: gatsby
- dependency-name: gatsby-remark-autolink-headers
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: gatsby
- dependency-name: gatsby-remark-copy-linked-files
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: gatsby
- dependency-name: gatsby-remark-prismjs
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: gatsby
- dependency-name: gatsby-remark-responsive-iframe
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: gatsby
- dependency-name: gatsby-remark-smartypants
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: gatsby
- dependency-name: gatsby-transformer-sharp
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: gatsby
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Peter Smulovics <[email protected]>