title: Select/copy hover text in R plotly graph
body: <p>I would like to be able to select and copy the hover text in plotly graphs. Is that possible with the R API?
  For example, in <a href="https://plot.ly/r/heatmaps/#categorical-axes" rel="noreferrer">this heatmap</a>, upon mousing over coordinates (X=a, Y=d), one can see the hover text displaying: </p>
  
  <p>x=a,</p>
  
  <p>y=d,</p>
  
  <p>z=0.71886</p>
  
  <p>However, the text is not selectable. The goal would be to <em>e.g.</em> display this text inside a box (perhaps by right-clicking on the corresponding cell) to be able to copy the text contents into the clipboard.
  Any help would be greatly appreciated.</p>