Add CSSStyleDeclaration injection API for parsed rule styles

[domenic]

Summary

• add a styleDeclarationProvider abstraction to resolve the declaration constructor used when creating rule style objects
• add public APIs in lib/index.js:
  • getCSSStyleDeclaration()
  • setCSSStyleDeclaration(CSSStyleDeclaration)
  • resetCSSStyleDeclaration()
• extend setup() to accept CSSStyleDeclaration and wire it via provider
• switch rule/clone construction sites to use the provider-backed constructor dynamically (avoids module load-order capture)
• keep existing optional cssstyle fallback behavior by routing it through the same provider
• document usage in README.mdown

Why

Consumers like jsdom need to inject their own CSSStyleDeclaration implementation. Reassigning require("@acemir/cssom/lib/CSSStyleDeclaration").CSSStyleDeclaration is not reliable because multiple modules capture constructor references during module initialization.

This PR provides an explicit integration point so parser-created rule declarations are consistently constructed with the consumer-provided class.

Validation

• npm run build
• runtime smoke checks from Node confirming:
  • default path still works
  • setup({ CSSStyleDeclaration }) causes parsed rule styles to use the injected constructor

[changeset-bot]

🦋 Changeset detected

Latest commit: e61c941

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

This PR includes changesets to release 1 package

Name	Type
@acemir/cssom	Minor

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[domenic]

This lets us remove the workaround from jsdom/jsdom#4089