build(deps-dev): bump eslint from 5.5.0 to 6.8.0

Bumps [eslint](https://github.com/eslint/eslint) from 5.5.0 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@v5.5.0...v6.8.0)

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

package.json

@@ -18,7 +18,7 @@
   "devDependencies": {
     "ava": "^1.0.1",
     "coveralls": "^3.0.0",
-    "eslint": "^5.0.0",
+    "eslint": "^6.8.0",
     "eslint-config-airbnb-base": "^12.0.0",
     "eslint-plugin-ava": "^6.0.0",
     "eslint-plugin-import": "^2.9.0",