title: How to change the default box decoration to rounded rectangular box for ExpansionPanelList widget of Flutter
body: <p>Flutter's expansion panel list (<a href="https://docs.flutter.io/flutter/material/ExpansionPanelList-class.html" rel="noreferrer">https://docs.flutter.io/flutter/material/ExpansionPanelList-class.html</a>) does not have a decoration. How to create a rounded edge expansion panel list? Please see the attached picture.</p>
  
  <p><img src="https://i.stack.imgur.com/YlJBP.png" alt="image with problem description"></p>