message: docs(readme): document changes in class names
diff: @@ -509,8 +509,8 @@ The React Flow wrapper has the className `react-flow`. If you want to change the
  ### Used Class Names
  * `.react-flow` - Outer container
  -* `.react-flow__renderer` - Inner container
  -* `.react-flow__zoompane` - Zoom & pan pane
  +* `.react-flow__renderer` - Flow container, used for zooming and panning
  +* `.react-flow__pane` - Background Pane for click and wheel events, previously `.react-flow__zoompane`
  * `.react-flow__selectionpane` - Selection pane
  * `.react-flow__selection` - User selection
  * `.react-flow__edges` - Edges wrapper
  