chore(deps-dev): bump rspress-plugin-sitemap from 1.1.1 to 1.2.0

Bumps [rspress-plugin-sitemap](https://github.com/jl917/rspress-plugin-sitemap) from 1.1.1 to 1.2.0.
- [Release notes](https://github.com/jl917/rspress-plugin-sitemap/releases)
- [Changelog](https://github.com/jl917/rspress-plugin-sitemap/blob/master/CHANGELOG.md)
- [Commits](jl917/rspress-plugin-sitemap@v1.1.1...v1.2.0)

---
updated-dependencies:
- dependency-name: rspress-plugin-sitemap
  dependency-version: 1.2.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]