add warning about unversioned cdn urls

[raju-opti]

No description provided.

[Copilot]

Pull Request Overview

This PR adds a warning to the README advising users to pin CDN URLs to specific versions to avoid unexpected breaking changes.

• Introduces a blockquote warning about unversioned CDN URLs
• References specifying versions (e.g., @6) in unpkg script tags

Comments suppressed due to low confidence (2)

README.md:134

• [nitpick] Consider specifying a full semantic version (e.g., @6.0.0) in the example to prevent unintended minor or patch upgrades, and update the example script tag accordingly.

> ⚠️ **Warning**: Always specify a version when using CDN URLs like `unpkg` URLs above (for example: `@6` in the examples above). Using unversioned CDN URLs can automatically pull in breaking changes when new versions are released, causing unexpected problems in the application.

README.md:134

• [nitpick] The warning currently mentions only unpkg. Consider generalizing this to include other CDNs (e.g., jsdelivr) or clarifying that the guidance applies to all CDNs for consistency.

> ⚠️ **Warning**: Always specify a version when using CDN URLs like `unpkg` URLs above (for example: `@6` in the examples above). Using unversioned CDN URLs can automatically pull in breaking changes when new versions are released, causing unexpected problems in the application.

[mikechu-optimizely]

LGTM