Fix `safeAreaInsets`

Use safeAreaInsets of window to avoid wrong insets caused by toolbar/tabbar.

Take Safe Area Insets Into Account

• Take safe area insets into account when laying out action sheet.
• Update example data.

Fix Crash Issue On iOS 11

Fix crash issue on iOS 11.

Swift Friendly

Added nullable annotation to be Swift friendly.

Allow Swift to Return nil in previewViewControllerForPopupPreviewRecognizer

Merge #2 (Allow Swift to return nil in previewViewControllerForPopupPreviewRecognizer)

First Release

• Long press to preview, release to dismiss.
• Slide up to show preview actions.