title: collapsible panels with overlay in border layout extjs
body: <p>I am using border layout with two panels in east and center as its items and by default if i make the east panel collapsible then it will resize the center panel when expanded or collapsed. I want to know if this nature can be changed in such a way that when the east panel is expanded , it overlays on the center panel rather than sharing the total width it.
  Below image might give some idea what i want to achieve.
  <img src="https://i.stack.imgur.com/MnleG.png" alt="enter image description here"></p>
  
  <p>thanks !</p>