title: How to add button to a messenger welcome screen?
body: <p>I have simple bot ,I want to set a greating text and add three buttons to it</p>
  
  <p>something like this.</p>
  
  <p>Welcom Johhn to man utd'</p>
  
  <p>-first button</p>
  
  <p>-second button</p>
  
  <p>-third button</p>
  
  <p>here is what I have tried</p>
  
  <pre><code>    $ curl -X POST -H "Content-Type: application/json" -d '{
      "greeting": [
        {
          "locale":"default",
          "text":"Hello {{user_first_name}}! Welcome to Man utd"
      message: {
            "attachment": {
            "type": "template",
            "payload": {
                "template_type": "generic",
                "elements": [{
                    "title": "Hi , thanks for messaging videommerce",
                    "buttons": [{
                        "type": "postback",
                        "title": "Select video purpose",
                        "payload": "purpose"
                    }, {
                        "type": "postback",
                        "title": "How to create video",
                        "payload": "create"
                    },{
                      "type": "web_url",
                      "url": "https://www.videommerce.com/",
                      "title": "Talk to us directly (moving to Customerly live chat)"
                    }],
                }]
            }
        }
          }
        }
     ]
    }' "https://graph.facebook.com/v2.6/me/messenger_profile?access_token=token"
  </code></pre>
  
  <p>What do I need to change to get what I want?</p>