Update dependency eslint-plugin-vue to v6 (#30)

Author: renovate[bot]

demo/package.json

@@ -20,7 +20,7 @@
     "@vue/cli-service": "^3.11.0",
     "babel-eslint": "^10.0.1",
     "eslint": "^5.16.0",
-    "eslint-plugin-vue": "^5.0.0",
+    "eslint-plugin-vue": "^6.0.0",
     "vue-cli-plugin-i18n": "^0.6.0",
     "vue-template-compiler": "^2.6.10"
   },