2.6.0

Bug Fixes and Improvements

• If a tree environment renders without an item defined as focused in its viewState parameter, it will invoke the onFocusItem
  prop with the first item in the tree during its render. In the past, this was implicitly and silently set in the viewState prop,
  now this assignment is triggered explicitly with the handler call (#363)
• Fixed a bug where an additional invalid drop target would be available at the bottom-most location when dragging via keyboard interactions (#363)