build(deps-dev): bump @vuepress/theme-default from 1.8.0 to 1.8.2 (#626)

Bumps [@vuepress/theme-default](https://github.com/vuejs/vuepress/tree/HEAD/packages/@vuepress/theme-default) from 1.8.0 to 1.8.2.
- [Release notes](https://github.com/vuejs/vuepress/releases)
- [Changelog](https://github.com/vuejs/vuepress/blob/master/CHANGELOG.md)
- [Commits](https://github.com/vuejs/vuepress/commits/v1.8.2/packages/@vuepress/theme-default)

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Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>