HWPanModal presents controller from bottom and drag to dismiss, high customize. iOS13 default modalPresentationStyle. 任意形式的底部弹框动画；头条、知乎、抖音弹出评论效果；地图浮层，iOS13 present默认模态效果。
fix different iOS version get keyWindow issue.
Fix crash: When delete datasource and reload data cause crash. Refer: https://github.com/HeathWang/HWPanModal/issues/103 https://github.com/HeathWang/HWPanModal/issues/107
add new API:
/**
* call this method to dismiss your presented VC directly
*/
- (void)hw_dismissAnimated:(BOOL)animated completion:(void (^)(void))completion NS_SWIFT_NAME(dismissAnimated(animated:completion:));
bug fix
- (BOOL)allowsPullDownWhenShortState;
improve allowsTouchEventsPassingThroughTransitionView api