Bump postcss-preset-env from 6.7.0 to 7.0.0 (#791)

Bumps [postcss-preset-env](https://github.com/csstools/postcss-preset-env) from 6.7.0 to 7.0.0.
- [Release notes](https://github.com/csstools/postcss-preset-env/releases)
- [Changelog](https://github.com/csstools/postcss-preset-env/blob/main/CHANGELOG.md)
- [Commits](https://github.com/csstools/postcss-preset-env/commits/7.0.0)

---
updated-dependencies:
- dependency-name: postcss-preset-env
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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