New features

• A Window.frame property was added.

Breaking changes

• The new Window.frame now uses Cocoa coordinates (origin at bottom-left), to match the behavior of Screen and most modern macOS APIs. See #29 for more.
• Window.position was removed in favor of Window.frame. See #32 for more.
• WindowFrameChangedEvent was added, replacing WindowPosChangedEvent and WindowSizeChangedEvent. See #16 for more.

Bug fixes

• ScreenLayoutChangedEvent is now correctly detected.
• When a property value is written to, and the new value is changed but does not match the desired value, the corresponding event is marked as external. See #49.