title: How to add custom column dynamically in ag-grid
body: <p>I'm stacked to add Custom columns dynamically in ag-grid.
  I have tried following approach.</p>
  
  <pre><code>additionalCol = { field:'SOME RANDOM', headerName: 'SOME RANDOM' };
  $scope.gridOptions.columnApi.addValueColumn(additionalCol);
  </code></pre>
  
  <p>I have also tried</p>
  
  <pre><code>$scope.columns.push(additionalCol);
  $scope.gridOptions.api.refreshView();
  </code></pre>
  
  <p>but didn't get success.
  I even tried to add columns that exist in Data but failed.
  Below is Image for what I am trying.
  <a href="https://i.stack.imgur.com/PQpvK.png" rel="noreferrer"><img src="https://i.stack.imgur.com/PQpvK.png" alt="enter image description here"></a></p>
  
  <p>As shown in image "% dev" is Custom column which I need to add dynamically with dynamically calculated values.</p>