title: Magento 2 custom rendered data not exporting
body: <p>I have created custom grid. All data is displayed in grid as expected. I need to export grid data in csv. data from main table is exported but its not exporting custom rendered data.</p>
  
  <p>e.g  all following columns in my listing.xml are displaying right data in grid. but in exported csv no data is displayed in postcode column, all values in csv for postcode column are blank.</p>
  
  <pre><code>    &lt;column name="created_at" class="Magento\Ui\Component\Listing\Columns\Date"&gt;
          &lt;argument name="data" xsi:type="array"&gt;
              &lt;item name="config" xsi:type="array"&gt;
                  &lt;item name="filter" xsi:type="string"&gt;dateRange&lt;/item&gt;
                  &lt;item name="component" xsi:type="string"&gt;Magento_Ui/js/grid/columns/date&lt;/item&gt;
                  &lt;item name="dataType" xsi:type="string"&gt;date&lt;/item&gt;
                  &lt;item name="label" xsi:type="string" translate="true"&gt;Purchase Date&lt;/item&gt;
              &lt;/item&gt;
          &lt;/argument&gt;
      &lt;/column&gt;
      &lt;column name="shipping_name"&gt;
          &lt;argument name="data" xsi:type="array"&gt;
              &lt;item name="config" xsi:type="array"&gt;
                  &lt;item name="filter" xsi:type="string"&gt;text&lt;/item&gt;
                  &lt;item name="label" translate="true" xsi:type="string"&gt;Name&lt;/item&gt;
              &lt;/item&gt;
          &lt;/argument&gt;
      &lt;/column&gt;
      &lt;column name="postcode" class="Vendor\Module\Ui\Component\Listing\Column\Reference"&gt;
          &lt;argument name="data" xsi:type="array"&gt;
              &lt;item name="config" xsi:type="array"&gt;
                  &lt;item name="filter" xsi:type="string"&gt;text&lt;/item&gt;
                  &lt;item name="label" translate="true" xsi:type="string"&gt;Postcode&lt;/item&gt;
              &lt;/item&gt;
          &lt;/argument&gt;
      &lt;/column&gt;
  </code></pre>
  
  <p>My grid
  <a href="https://i.stack.imgur.com/x83jv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/x83jv.png" alt="enter image description here"></a></p>
  
  <p>My csv
  <a href="https://i.stack.imgur.com/f9Vcd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/f9Vcd.png" alt="enter image description here"></a></p>