Implement 'selected' and 'disabled' accessibilityState

[jonthysell]

We need to map these accessibilityState values to XAML properties:

• selected -> IsSelected https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.automation.selectionitempatternidentifiers.isselectedproperty
• disabled -> IsEnabled https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.automation.automationelementidentifiers.isenabledproperty