Update vue-i18n requirement from 8.7.0 to 8.8.0

Updates the requirements on [vue-i18n](https://github.com/kazupon/vue-i18n) to permit the latest version.
- [Release notes](https://github.com/kazupon/vue-i18n/releases)
- [Changelog](https://github.com/kazupon/vue-i18n/blob/dev/CHANGELOG.md)
- [Commits](https://github.com/kazupon/vue-i18n/commits/v8.8.0

)

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