延迟系统手势，直到第二次滑动特定边缘。
On iPhone X the home button is implemented as a system gesture (swipe up from the lower edge of the screen).
Other gestures are implemented as swipes from other screen edges.
This may interfere with games that use swipes as an interaction method.
This setting specifies which screen edge gestures the system defers to the second swipe.
The first swipe is ignored and provides a way to reduce unwanted interactions with the App.
iOS Human interface guidelines don't recommend enabling this behavior as it might confuse users.
The value of this property can be changed on runtime by setting PlayerSettings.iOS.deferSystemGesturesMode property.
Note: Setting PlayerSettings.iOS.hideHomeButton to true will cause deferSystemGesturesMode to fail.
This is due to the home button on an iPhone X being a system gesture in itself.