Consider a scenario where the background color and indicator's background color are the same. 

Adding a stroke color to the value indicator would be a valuable for the following reasons:
- **Visual Clarity:** It would allow developers to make the value indicator stand out more against the background, making it easier for users to notice.
- **Customization:** It would provide more flexibility in customizing the appearance of the sliding widget, allowing developers to match the design requirements of their apps.
- **Accessibility:** Improved visual distinction can enhance the accessibility of the sliding widget for users with various needs.

*List which issues are fixed by this PR. You must list at least one issue.*

Fixes #135984