Bump eslint-config-eslint from 5.0.1 to 6.0.0 in /addon (#34)

Bumps [eslint-config-eslint](https://github.com/eslint/eslint) from 5.0.1 to 6.0.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](https://github.com/eslint/eslint/compare/v5.0.1...v6.0.0)

---
updated-dependencies:
- dependency-name: eslint-config-eslint
  dependency-type: direct:development
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

addon/package.json

@@ -31,7 +31,7 @@
   },
   "devDependencies": {
     "eslint": "^6.4.0",
-    "eslint-config-eslint": "^5.0.1",
+    "eslint-config-eslint": "^6.0.0",
     "eslint-config-google": "^0.14.0",
     "eslint-plugin-node": "^10.0.0"
   }