chore(deps-dev): bump vuepress from 1.3.0 to 1.3.1
Bumps [vuepress](https://github.com/vuejs/vuepress/tree/HEAD/packages/vuepress) from 1.3.0 to 1.3.1.
- [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/v1.3.1/packages/vuepress)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>