Add support for native `@supports` at-rule creation for feature queries

[alexgrozav]

Summary

Add native support for generating CSS @supports at-rules within the Styleframe TypeScript CSS API, allowing developers to use feature queries for progressive enhancement and browser compatibility.

Motivation

Feature queries using the @supports at-rule enable conditional CSS based on browser support for specific features. This is important for writing robust, future-proof design systems code with Styleframe.

Proposed Implementation

• Expose an API to define CSS feature queries using the native @supports at-rule.
• Ensure generated stylesheets include the correct feature query syntax and integrate with other Styleframe features.
• Add documentation and usage examples for the new API.

References

• MDN: CSS @supports

Acceptance Criteria

• Ability to create and compose feature queries using Styleframe.
• Type-safe API for feature query creation.
• Tests and documentation updated.

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Repository language: TypeScript