Add an Example of PropertyChanged Handler

It would be helpful to include a basic example of how to implement a hander. Something like this:
PropertyChanged += (sender, e) =>
{
Console.WriteLine($"Property: {e.PropertyName} changed.");
};

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#### Document Details

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* ID: a0965a46-4e23-9280-7bef-915efe44b20d
* Version Independent ID: b48f8b3a-3486-a11c-7422-fcb7874ab6ad
* Content: [INotifyPropertyChanged Interface (System.ComponentModel)](https://docs.microsoft.com/en-us/dotnet/api/system.componentmodel.inotifypropertychanged?view=netframework-4.7.2)
* Content Source: [xml/System.ComponentModel/INotifyPropertyChanged.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.ComponentModel/INotifyPropertyChanged.xml)
* Product: **dotnet-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **dotnetcontent**