build(deps-dev): update eslint requirement from ^5.1.0 to ^6.2.1

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@v5.1.0...v6.2.1)

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

package.json

@@ -53,7 +53,7 @@
     "coveralls": "^3.0.0",
     "dependency-check": "^4.1.0",
     "documentation": "^12.0.0",
-    "eslint": "^5.1.0",
+    "eslint": "^6.2.1",
     "eslint-plugin-import": "^2.8.0",
     "eslint-plugin-mocha": "^6.0.0",
     "husky": "^3.0.0",