Add eslint config.

package.json

@@ -22,5 +22,24 @@
     "eslint-plugin-prettier": "^3.1.3",
     "eslint-plugin-vue": "^7.0.0-0",
     "prettier": "^1.19.1"
-  }
+  },
+  "eslintConfig": {
+    "root": true,
+    "env": {
+      "node": true
+    },
+    "extends": [
+      "plugin:vue/vue3-essential",
+      "eslint:recommended"
+    ],
+    "parserOptions": {
+      "parser": "babel-eslint"
+    },
+    "rules": {}
+  },
+  "browserslist": [
+    "> 1%",
+    "last 2 versions",
+    "not dead"
+  ]
 }