docs(StatusBar): add guidance for setting StatusBar on every page

[vatsashah45]

GitHub Issue (If applicable): closes https://github.com/unoplatform/uno.ai-private/issues/430

PR Type

What kind of change does this PR introduce?

• Documentation content changes

What is the current behavior?

What is the new behavior?

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Tested the changes where applicable:
  • UWP
  • WinUI
  • iOS
  • Android
  • WASM
  • MacOS
• Updated the documentation as needed:
  • General Doc Update
  • Controls Doc Update
  • Extensions Doc Update
  • controls-styles.md
  • lightweight-styling.md (LightWeight Styling Resource Keys)
• Runtime Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Contains NO breaking changes
• Associated with an issue (GitHub or internal)
• Commits must be following the Conventional Commits specification.

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[kazo0]

I'm not sure this is necessarily correct. This one I'm not sure about actually.

Could we instead add something, conditionally on Toolkit being present, to the mcp rules init that StatusBar should be used and default Foreground to Auto and default Background to the Page's Background (may not always be ApplicationPageBackgroundThemeBrush, could be BackgroundBrush with Material, etc.)