Bump vuex from 3.0.1 to 3.1.0 (#63)

Bumps [vuex](https://github.com/vuejs/vuex) from 3.0.1 to 3.1.0.
- [Release notes](https://github.com/vuejs/vuex/releases)
- [Commits](vuejs/vuex@v3.0.1...v3.1.0)

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