title: error: Do not use Array index in keys
body: <p>I am using index to generate key in a list. However, es-lint generates an error for the same. React <a href="https://reactjs.org/docs/lists-and-keys.html" rel="noreferrer">doc</a> also states that using the item index as a key should be used as last resort. </p>
  
  <pre><code>const list = children.map((child, index) =&gt;
      &lt;li key={index}&gt; {child} &lt;/li&gt;);
  </code></pre>
  
  <p>I considered using <code>react-key-index</code>. 
  <code>npm install react-key-index</code> gives following error:</p>
  
  <p><code>npm ERR! code E404</code></p>
  
  <p><code>npm ERR! 404 Not Found: react-key-index@latest</code></p>
  
  <p>Are there any suggestions on other packages that allow to generate unique key? Any suggestion on react key generator is appreciated!</p>