Support `background-clip` property rendering in web content renderer

[yorkie]

Feature Request

Implement support for the background-clip CSS property in the web content renderer, with a particular focus on enabling background-clip: text rendering effects. This would allow background images or gradients to be clipped to the foreground text, which is a widely used modern web design feature.

Expected Behavior

• The renderer should correctly interpret and render the background-clip property for elements.
• For background-clip: text, the background should be visible only where the text glyphs are present, following the CSS specification.
• Should work for both solid color and gradient/image backgrounds.

References

• MDN: background-clip
• CSS Tricks: Background Clip Text

Motivation

Enabling this feature will allow more visually rich and modern web content in JSAR, improving parity with mainstream browsers.