Changes

• Adds an Embed Block that renders external content based on the block's OEmbed data.
  • Supports ~300 content providers (like Twitter, Flickr, YouTube, etc) using the OEmbed protocol.
  • Renders a noscript embed version which is dynamically enhanced.
  • Lazy loads embed scripts and iframes to improve performance.
  • Provides a mechanism to define custom renderer per provider.
  • Adds specific implementations for Twitter, YouTube and Vimeo (the last two reusing the Video Embed Block).
  • If OEmbed data is unavailable, a link is displayed with the page title of the given URL.
  • Embed Block data is preloaded in the CMS using the DatoCMS OEmbed Plugin.

Associated issue

Resolves #107

How to test

1. Open preview link
2. Navigate to page with embeds
3. Verify the different embeds are rendered correctly
4. Verify embeds are lazy loaded when scrolled into view
5. Verify embeds show a basic (non-enhanced) version when JS is disabled
6. Review Embed Block model in the CMS
7. Add an Embed Block to a page
8. Verify a preview is displayed and the embed data is set
9. Verify the new embed is rendered on the page

Checklist

• I have performed a self-review of my own code
• I have made sure that my PR is easy to review (not too big, includes comments)
• I have made updated relevant documentation files (in project README, docs/, etc)
• I have added a decision log entry if the change affects the architecture or changes a significant technology
• I have notified a reviewer