add data to flexdashboard code example

Example: how to set JSON data bootstrap treeview with java

var withText = jsondata.map(function(i) {
    i['text'] = i['bibliography_text'];
    return i;
  });

  var nestedData = d3.nest()
    .key(function(d) { return d.country; })
    .key(function(d) { return d.city; })
    .entries(withText);