Update eslint requirement from ^5.14.1 to ^6.1.0

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@v5.14.1...v6.1.0)

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

package.json

@@ -28,7 +28,7 @@
   },
   "devDependencies": {
     "chai": "^4.2.0",
-    "eslint": "^5.14.1",
+    "eslint": "^6.1.0",
     "eslint-config-hexo": "^3.0.0",
     "mocha": "^6.0.1",
     "nyc": "^14.1.1"