title: Angular formly multicheckbox
body: <p>I have been looking for an example for 'multicheckbox' type in 'angular formly form', where the check-boxes are selected or unselected based on corresponding value in form model, when the form is loaded,but could not find any.Can some one please help me with an example?</p>
  
  <p>I shall explain my exact case :</p>
  
  <p>Following is my formly form.Its a multicheckbox with key as 'selectedAnswer'.Initial value for 'selectedAnswer' in the forms model is "ee,dd".But the correspondig values are not getting checked in the check box on loading the form. </p>
  
  <pre><code>[
     {
        "key":"selectedAnswer",
        "type":"multiCheckbox",
        "templateOptions":{
           "label":"fsdfsdf",
           "options":[
              {
                 "name":"ee",
                 "value":"ee"
              },
              {
                 "name":"dd",
                 "value":"dd"
              },
              {
                 "name":"tg",
                 "value":"tg"
              }
           ]
        }
     }
  ]
  </code></pre>
  
  <p>Please help me to fix this issue.
  Thanks,
  Deepthy.</p>