Create default style for StatusBar control #3926

Right now the library does not implement any styling for the WPF StatusBar control.

WPF Docs showing a sample style/template:
https://learn.microsoft.com/dotnet/desktop/wpf/controls/statusbar-styles-and-templates

• Add default style for the StatusBar control. The style and contorl template should be in a file named "src\MaterialDesignThemes.Wpf\Themes\MaterialDesignTheme.StatusBar.xaml"
• Should use theme brushes to support light and dark themes
• Sample page should be added to the MD2 demo app