title: How use [optionalTrackingData] with viber-bot
body: <p>I want to get some extra data from the user in my viber bot. This can be done via [optionalTrackingData]. But no matter how hard I try to send a message with [optionalTrackingData], the message from the user is always empty. Maybe there are some additional settings? I write on Node.js</p>
  <p>this what I tried:
  bot.sendMessage(response.userProfile, [
  new TextMessage(&quot;please select your email:&quot;),
  keyboardMessage
  ], {'trackingData':'trackingData'});</p>
  <p>please help</p>