title: display information in network edges using visNetwork
body: <p>I am starting to learn about interactive graphs in R, and  I found the library <code>visNetwork</code> very helpful.</p>
  
  <p>However, I don't find on the vignettes how to display a pop-up with more information than the <code>value</code> and <code>title</code> when the mouse is moved over the edge.</p>
  
  <p>Using one of the examples in the documentation</p>
  
  <pre><code># data used in visNetwork vignette
  nb &lt;- 10
  nodes &lt;- data.frame(id = 1:nb, label = paste("Label", 1:nb),
  group = sample(LETTERS[1:3], nb, replace = TRUE), value = 1:nb,
  title = paste0("&lt;p&gt;", 1:nb,"&lt;br&gt;Tooltip !&lt;/p&gt;"), stringsAsFactors = FALSE)
  
  edges &lt;- data.frame(from = c(8,2,7,6,1,8,9,4,6,2),
  to = c(3,7,2,7,9,1,5,3,2,9),
  value = rnorm(nb, 10), label = paste("Edge", 1:nb),
  title = paste0("&lt;p&gt;", 1:nb,"&lt;br&gt;Edge Tooltip !&lt;/p&gt;"))
  
  visNetwork(nodes, edges, height = "500px", width = "100%") 
  </code></pre>
  
  <p>How could I add more information to the pop-up, such as, different parameters related to the edge (width, frequency, ..)?</p>