Status bar foreground doesn't change with change in theme! #530

Description
StatusBarItem foreground stays "black" when theme is switched from light to dark.

To Reproduce
Steps to reproduce the behavior:

1. Create a HandyControls project in Visual Studio 2019.
2. Add light, dark and voilet themes to the app.
3. In MainWindow xaml add a StatusBar.
4. Then to this StatusBar add a StatusBarItem and set it's content.
5. Now run the app. And change the theme between light and dark or violet. You'll notice when the theme has been changed to dark from light the StatusBarItem's foreground does not change from black to white.

Expected behavior
When the theme has changed from light to dark I expect the StatusBarItem's foreground to change from black to white.

Environment:

• .net: [e.g. 4.7.2]
• IDE [vs2019]
• Version [e.g. 16.8.2]

All other controls I've add to the app change their foreground as expected when the theme changes.