Update polyfill JS example (#1958)
Update polyfill JS example (#1958)

- Update Polyfill CDN to v2 which is the default version (Ref: https://cdn.polyfill.io )
- Switch the JQuery from Google's CDN to Jquery's CDN to match the main index.html
- Update to jQuery 3.2.1.
- Add SRI hash to jQuery link
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