title: Empty Plotly with centered title R
body: <p>I am trying to create an empty <code>plotly</code> with a message telling why the plot is empty as a title. I would like to center the message both horizontally and vertically.</p>
  
  <p>I am missing the vertical center :</p>
  
  <pre><code>empty_plot &lt;- function(title = NULL){
    p &lt;- plotly_empty(type = "scatter", mode = "markers") %&gt;%
      config(
        displayModeBar = FALSE
      ) %&gt;%
      layout(
        title = title
      )
    return(p)
  }
  
  empty_plot("Why it is empty")
  </code></pre>