builde(deps-dev): allow ESLint ^6 too

Author: Kocal

package.json

@@ -66,7 +66,7 @@
     "chai-fs": "^1.0.0",
     "chai-subset": "^1.6.0",
     "core-js": "^3.0.0",
-    "eslint": "^5.15.2",
+    "eslint": ">=5.15.2",
     "eslint-loader": "^2.1.2",
     "eslint-plugin-header": "^1.0.0",
     "eslint-plugin-import": "^2.8.0",