chore(deps): bump webpack-dev-middleware and gatsby in /site

Bumps [webpack-dev-middleware](https://github.com/webpack/webpack-dev-middleware) to 5.3.4 and updates ancestor dependency [gatsby](https://github.com/gatsbyjs/gatsby). These dependencies need to be updated together.


Updates `webpack-dev-middleware` from 4.3.0 to 5.3.4
- [Release notes](https://github.com/webpack/webpack-dev-middleware/releases)
- [Changelog](https://github.com/webpack/webpack-dev-middleware/blob/v5.3.4/CHANGELOG.md)
- [Commits](webpack/webpack-dev-middleware@v4.3.0...v5.3.4)

Updates `gatsby` from 5.12.9 to 5.14.0
- [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/[email protected]@5.14.0)

---
updated-dependencies:
- dependency-name: webpack-dev-middleware
  dependency-type: indirect
- dependency-name: gatsby
  dependency-type: direct:production
...

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

Author: dependabot[bot]