Offer a scoped option

I often work on SPA starter templates. To keep package.json dependencies light, I use CDN for the bundled examples.

Unfortunately when using `Open Props` this leaves me with two options.
1. **CDN** - The styling bleeds into the user's code.
2. **NPM** and `node props.js '' true '.starter-examples'` - This adds dependencies to package.json that the user might not want.

If Open Props had a scoped CDN option, like `where(.open-props)`, it would be very simple to keep the project lean while styling specific elements without bleeding into the user's code.

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Thanks for a great library!

Start by tracing the `node props.js '' true '.starter-examples'` entry point and how the CDN bundle is produced. Compare the current global CDN behavior with the requested `.open-props` scope, and verify that the result styles only scoped elements without adding unwanted package.json dependencies.

Written by the indexing model from the issue text.