title: How to make a full width render on ReferenceManyField?
body: <p>I have a <code>react-admin</code> show page configured with some <code>ReferenceManyField</code> components like this one:</p>
  <pre class="lang-js prettyprint-override"><code>&lt;ReferenceManyField
    reference=&quot;children&quot;
    target=&quot;userId&quot;
    label=&quot;Enfants&quot;
  &gt;
    &lt;Datagrid
      rowClick=&quot;edit&quot;
    &gt;
      &lt;TextField
        source=&quot;lastName&quot;
        label=&quot;Nom&quot;
      /&gt;
      &lt;TextField
        source=&quot;firstName&quot;
        label=&quot;Prénom&quot;
      /&gt;
      &lt;DateField
        source=&quot;birthday&quot;
        label=&quot;Date de naissance&quot;
        showTime={false}
      /&gt;
      &lt;TextField
        source=&quot;phoneNumber&quot;
        label=&quot;Tél.&quot;
      /&gt;
    &lt;/Datagrid&gt;
  &lt;/ReferenceManyField&gt;
  </code></pre>
  <p>It works, but the rendered tab are content sized:</p>
  <p><a href="https://i.stack.imgur.com/CL5eS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CL5eS.png" alt="Reference array table render" /></a></p>
  <p>My question is quite simple: How to make it full width?</p>
  <p>I tried the <code>fullWidth</code> option on <code>ReferenceManyField</code> without any effect.</p>