title: How to add toggleSelectAll functionality checkbox to new header which is generated by header slot
body: <p>I tried to customize vuetify data table header with slot.
  I disabled default header and made a new header with <code>v-slot:header</code>.
  The problem is that if I make new header, there is no checkbox which support toggleSelectAll functionality.
  The code is below.</p>
  <pre><code>&lt;template
    v-slot:header=&quot;{ props: { headers } }&quot;
  &gt;
    &lt;thead&gt;
      &lt;tr&gt;
        &lt;th v-for=&quot;header in headers&quot; :key=&quot;header.value&quot;&gt;
          &lt;v-simple-checkbox
            color=&quot;purple&quot;
            v-if=&quot;header.value === 'data-table-select'&quot; 
          &gt;&lt;/v-simple-checkbox&gt;
          &lt;span v-else&gt;{{header.text}}&lt;/span&gt;
        &lt;/th&gt;
      &lt;/tr&gt;
    &lt;/thead&gt;
  &lt;/template&gt;
  </code></pre>
  <p>And here is the Codepen link.
  <a href="https://codepen.io/em0809/pen/gOrJGjJ" rel="nofollow noreferrer">https://codepen.io/em0809/pen/gOrJGjJ</a></p>
  <p>I want to add toggleSelectAll functionality to above simple checkbox.
  I tried with <code>v-slot:header.data-table-select</code>, but it's not working.</p>
  <p>So, Please help me with this if you have experience.</p>
  <p>Thank you.</p>