Doc Alignment: Add richer samples for Flyout, Slider pages

[stmoy]

Describe the bug

For both the Flyout and Slider pages, it'd be worthwhile to have a sample that shows the controls "in context" similar to what is shown on the docs site.

Flyout: https://docs.microsoft.com/en-us/windows/uwp/design/controls-and-patterns/dialogs-and-flyouts/flyouts

(For Flyout specifically, it'd also be valuable to show an example of the 10 foot experience: https://docs.microsoft.com/en-us/windows/uwp/design/controls-and-patterns/dialogs-and-flyouts/flyouts#styling-flyouts-for-10-foot-experiences)

Slider: https://docs.microsoft.com/en-us/windows/uwp/design/controls-and-patterns/slider#examples