Bump eslint from 4.19.1 to 6.8.0

Bumps [eslint](https://github.com/eslint/eslint) from 4.19.1 to 6.8.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](eslint/eslint@v4.19.1...v6.8.0)

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

Author: dependabot-preview[bot]