Add the option to customize the window picker presentation config

[EchoEllet]

• The plugin presents the PHPickerViewController as a sheet, it could also be displayed as a modal window (presentAsSheet or presentAsModalWindow). Provide an enum to allow overriding this.
• The sheet minimum and initial size are hardcoded by setting a frame to the PHPickerViewController's view. The behavior is similar to the default behavior when displaying the picker using PhotosPicker in a macOS SwiftUI app. Provide a config class to allow overriding the default.
• See if there are any other properties that clients might want to override to fit the requirements.