title: R plotly subplot add space between plots
body: <p>I want to add space between plots but when I play with margin, it either overlaps or cuts.
  Here is the code:</p>
  
  <pre><code>library(plotly)
  
  plotList &lt;- function(nplots) {
    lapply(seq_len(nplots), function(x) plot_ly())
  }
  s1 &lt;- subplot(plotList(6), nrows = 2, shareX = TRUE, shareY = TRUE)
  s2 &lt;- subplot(plotList(2), shareY = TRUE)
  p &lt;- subplot(s1, s2, plot_ly(), nrows = 3, margin = 0.04, heights = c(0.6, 0.3, 0.1))
  
  print(p)
  </code></pre>
  
  <p>I obtain this:</p>
  
  <p><a href="https://i.stack.imgur.com/T8TzU.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/T8TzU.jpg" alt="enter image description here"></a></p>
  
  <p>Whereas i would rather like something like this (image done with paint) with more spacing between the different subplots:</p>
  
  <p><a href="https://i.stack.imgur.com/Y25aY.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/Y25aY.jpg" alt="enter image description here"></a></p>
  
  <p>How should I do ?</p>