title: multiple selection inside the drop down menu in flutter
body: <p>Hi In my App I have something like this.</p>
  
  <p><a href="https://i.stack.imgur.com/MJu2L.png" rel="noreferrer"><img src="https://i.stack.imgur.com/MJu2L.png" alt="this"></a> </p>
  
  <p>where I have a dropdown which displaying 3 options, but is there any way I can select multiple options inside the dropdown in flutter? and to store the result of selected options inside the list?</p>
  
  <p>or is it possible to do something like below in flutter?</p>
  
  <p><a href="https://i.stack.imgur.com/4K683.png" rel="noreferrer"><img src="https://i.stack.imgur.com/4K683.png" alt="enter image description here"></a></p>
  
  <p>Thanks.</p>