reorderable_grid_view 1.1.0-alpha.4

reorderable_grid_view: ^1.1.0-alpha.4 copied to clipboard

• support alpha.3. For the merge mistake.

• update dragWidgetBuilder(child) to dragWidgetBuilder(index, child)

• add option dragWidgetBuilder, can config custom drag widget.
• add option scrollSpeedController, can config the scroll speed.

• fix childAspectRatio bug

• use new impl correspond to new reorderable_listview impl
• add drag scroll ability
• deprecate option antiMultiDrag

• add null-safety
• add option antiMultiDrag

• add GridView construct params, like physics etc.

fix add footer issue

fix grid gap, calculate item position issue.

• TODO: Describe initial release.