Update eslint requirement from ^5.16.0 to ^6.0.1

Updates the requirements on [eslint](https://github.com/eslint/eslint) to permit the latest version.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](eslint/eslint@v5.16.0...v6.0.1)

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

Author: dependabot-preview[bot]

package.json

@@ -35,7 +35,7 @@
   },
   "devDependencies": {
     "chai": "^4.1.2",
-    "eslint": "^5.16.0",
+    "eslint": "^6.0.1",
     "eslint-config-hexo": "^3.0.0",
     "iferr": "^1.0.2",
     "istanbul": "^0.4.5",