Bump tmp and gatsby

Bumps [tmp](https://github.com/raszi/node-tmp) to 0.2.5 and updates ancestor dependency [gatsby](https://github.com/gatsbyjs/gatsby). These dependencies need to be updated together.


Updates `tmp` from 0.2.1 to 0.2.5
- [Changelog](https://github.com/raszi/node-tmp/blob/master/CHANGELOG.md)
- [Commits](raszi/node-tmp@v0.2.1...v0.2.5)

Updates `gatsby` from 2.24.78 to 5.15.0
- [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/gatsby@2.24.78...gatsby@5.15.0)

---
updated-dependencies:
- dependency-name: tmp
  dependency-version: 0.2.5
  dependency-type: indirect
- dependency-name: gatsby
  dependency-version: 5.15.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]