title: How to use `DT::renderDT()` with both `option` argument and `formatCurrency()`
body: <p>I have a table displayed within a Shiny application using <code>DT::renderDT()</code> like so:</p>
  <pre><code>DT::renderDT(tab %&gt;% 
              selection = &quot;none&quot;,
              extensions = 'Buttons',
              option = list(buttons = c('copy', 'csv', 'excel', 'pdf', 'print'),
                            dom = 'Brti')
            )
  </code></pre>
  <p>and then I wanted to use the <code>formatCurrency()</code> function as well:</p>
  <pre><code>DT::renderDT(DT::datatable(tab) %&gt;% 
                DT::formatCurrency(columns = 2:5, 
                                   currency = '',                                 
                                   mark = &quot; &quot;,
                                   digits = 0),
              selection = &quot;none&quot;, 
              extensions = 'Buttons',
              option = list(buttons = c('copy', 'csv', 'excel', 'pdf', 'print'),
                            dom = 'Brti')
            )
  </code></pre>
  <p>and get the following warning:
  <code>Warning in processWidget(instance) : renderDataTable ignores ... arguments when expr yields a datatable object; see ?renderDataTable</code>
  i.e. I can't provide both the <code>datatable()</code> object itself and the <code>renderDT()</code> with options.</p>
  <p>Unfortunately I didn't find the way of using the <code>formatCurrency()</code> function directly within the <code>DT::renderDT()</code> function, can anyone tell me how I should do that?</p>