title: no-use-before-define has no effect when extending eslint-config-react-app
body: <p>I am trying to configure eslint to use <code>eslint-config-react-app</code> as a base and specify a few specific rules on top of that. One of those rules is <code>no-use-before-define</code>, and I am trying this out on the following trivial example to check whether the rule is working as desired:</p>
  <pre class="lang-js prettyprint-override"><code>const a = () =&gt; {
      b();
  };
  const b = () =&gt; {};
  a();
  </code></pre>
  <p>If I set up my .eslintrc.json like this, then the rule works as expected:</p>
  <pre class="lang-json prettyprint-override"><code>{
      &quot;parserOptions&quot;: {
          &quot;ecmaVersion&quot;: 2020
      },
      &quot;rules&quot;: {
          &quot;no-use-before-define&quot;: &quot;error&quot;
      }
  }
  </code></pre>
  <pre><code>2:5  error  'b' was used before it was defined  no-use-before-define
  </code></pre>
  <p>However, if I include <code>&quot;extends&quot;: &quot;react-app&quot;</code>, no eslint errors are found:</p>
  <pre class="lang-json prettyprint-override"><code>{
      &quot;extends&quot;: &quot;react-app&quot;,
      &quot;parserOptions&quot;: {
          &quot;ecmaVersion&quot;: 2020
      },
      &quot;rules&quot;: {
          &quot;no-use-before-define&quot;: &quot;error&quot;
      }
  }
  </code></pre>
  <p>If I intentionally introduce a change that would cause another eslint violation - e.g. remove the <code>a();</code> a the end, then <em>that</em> is found, but not the <code>no-use-before-define</code> violation:</p>
  <pre><code>  1:7  warning  'a' is assigned a value but never used  no-unused-vars
  </code></pre>
  <p>Intuitively, I would expect any rules in .eslintrc.json to be applied <em>on top of</em> the config indicated in <code>&quot;extends&quot;</code>, but it seems like that's not what's happening.</p>
  <p>What am I misunderstanding here? Is there a way to extend <code>eslint-config-react-app</code> <em>and</em> have the <code>no-use-before-define</code> rule work correctly?</p>