title: how to wordwrap a header in ag-grid
body: <p>Using ag-grid, is there a way to split a long header across 2 rows...</p>
  
  <p>A break in the columnDefs headerName: <code>'Long&lt;br /&gt;Header'</code>
  gets me part way there (using dev tools I can see the text has the br), however one of the surrounding elements has a height of 25px; <code>&lt;div class="ag-header" style="height: 25px;"&gt;</code> which I think causes the second line of the header to not be displayed.</p>
  
  <p>I wondered about using group headers as an interim to get the text split, but longer term (when I need to group) that won't be an option...</p>