build(deps-dev): bump eslint from 6.3.0 to 6.4.0

Bumps [eslint](https://github.com/eslint/eslint) from 6.3.0 to 6.4.0.
- [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/v6.3.0...v6.4.0)

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

package.json

@@ -31,7 +31,7 @@
     "xmlhttprequest": "^1.8.0"
   },
   "devDependencies": {
-    "eslint": "^6.3.0",
+    "eslint": "^6.4.0",
     "jest": "^24.9.0"
   }
 }