title: add custom boxshadow to Flutter card
body: <p>I've implemented cards in a Flutter app. I need a custom <code>BoxShadow</code> for every card. How can this be done?</p>
  
  <p>What I've tried so far is to add the <code>BoxShadow</code> property to the <code>Card()</code> constructor, which is not working...</p>