Add utils/color for css color-mix

[seongminn]

Added a color utility to enable type-safe usage of the CSS color-mix() function. It provides a chaining API consistent with the existing calc utility.

Key Changes

• Supports all standard Color Spaces (e.g., srgb, oklch, lab, hsl).
• Supports Hue Interpolation Methods (shorter, longer, increasing, decreasing).
• Adopts a chaining pattern and factory structure similar to calc.
• Generates valid color-mix() syntax strings.

[changeset-bot]

🦋 Changeset detected

Latest commit: 404760a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@vanilla-extract/css-utils	Minor

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