[@mantine/core] Button: Native tooltip for button

[WojakGra]

This pull request introduces a new demo showcasing how to implement a native CSS tooltip for a button using modern CSS Anchor Positioning features. The new example is integrated into the documentation, complete with both TypeScript and CSS code, and is now available in the Button component demos. This provides users with an alternative to JavaScript-based tooltips, while also explaining browser support caveats.

New Native CSS Tooltip Demo:

• Added a new demo component, Button.demo.nativeTooltip.tsx, which demonstrates a tooltip positioned with CSS Anchor Positioning and includes both the React and CSS code needed for the example.
• Created a corresponding CSS module, Button.demo.nativeTooltipStyles.module.css, defining the tooltip's positioning, appearance, and show/hide behavior on hover using anchor positioning properties.

Documentation and Integration:

• Updated the Button documentation (button.mdx) to include a new section explaining the native CSS tooltip approach, its limitations, and when to use the built-in Tooltip component instead.
• Registered the new demo in the Button demos story file, making it available in the demo explorer.
• Exported the new demo from the Button demos index for use in documentation and stories.