Set or get the sash gravity. Gravity is a value between 0 and 100 which controls the position
of the sash while resizing the splitter group. The gravity value tells splitter group how much
the top child will grow while resizing. For example:
- – 0: Only the bottom child is automatically resized.
- – 50: Both children grow by equal size.
- – 100: Only the top child grows.
The default sash gravity is 0.