title: How i can get warning instead of error in ESLint for no-unused-vars?
body: <p>How I can get a warning instead of an error while using ESLint?</p>
  
  <p>I use ESLint <code>6.7.2</code> version with a plugin for babel and react.</p>
  
  <p>This is my actual <code>.eslintrc.json</code>:</p>
  
  <pre><code>{
      "env": {
          "browser": true,
          "es6": true
      },
      "extends": [
          "eslint:recommended",
          "plugin:react/recommended"
      ],
      "globals": {
          "Atomics": "readonly",
          "SharedArrayBuffer": "readonly"
      },
      "parserOptions": {
          "ecmaFeatures": {
              "jsx": true
          },
          "ecmaVersion": 2018,
          "sourceType": "module"
      },
      "plugins": [
          "react"
      ],
      "rules": {
      },
      "settings": {
          "react" : {
              "version": "16.7.0"
          }
      },
      "parser": "babel-eslint"
  }
  </code></pre>