docs: document quicklink.modern.mjs bundle

[sankalpsthakur]

Summary

• Documents the quicklink.modern.mjs build in README.md and the site usage section.
• Notes when to prefer it (modern browsers / native ES modules; smaller, no legacy transforms) and includes an import example.

Fixes #385

Validation

• Confirmed dist/quicklink.modern.mjs is produced by the microbundle build and tracked in .size-limit.json.
• Docs-only change; no code or build changes.

AI/LLM disclosure

• AI coding tools (including Grok and/or Codex agent-assisted editing) were used to help draft or modify code and this PR description.
• I reviewed the complete change, understand the reasoning, and ran the reported local tests before submitting.
• This submission is original work of authorship under the project CLA / contributor terms; AI output was not pasted unreviewed.

Made with Cursor

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[addyosmani]

Clear and accurate — rollup (via #463) still emits quicklink.modern.mjs, so this guidance holds. FYI I rebased your branch onto main to drop a stray merge commit that was tripping the CLA check; your commit is untouched. Thanks for documenting this. 👍