title: How to add a member to rapidjson whose value is NULL?
body: <p>Is there a neat way to add a member to a RapidJson document object?</p>
  
  <p>As a workaround, I added a random string to the document and then set it to NULL.</p>
  
  <pre><code>  rapidJson::Document doc;
    doc.SetObject();
    doc.AddMember("MemberWhoseValueIsNULL", "randomString");
    doc["MemberWhoseValueIsNULL"].SetNull();
  </code></pre>
  
  <p>I was wondering if there is a better way to do this?</p>