Acceptance Criteria

• The listed features are documented sufficiently on MDN
• BCD is updated
• Interactive example and data repos are updated if appropriate
• The content has been reviewed as needed

For folks helping with Firefox related documentation

• Set bugs to dev-doc-complete
• Add entry to Firefox release notes if feature is enabled in release
  or
• Add entry to Firefox experimental features page if feature is not yet enabled in release

Features to document

(intersection-observer) Chrome allows an empty string for rootMargin, Firefox throws an exception, breaking some shopping sites. Probably just a note in BCD & checking docs

Related Gecko bugs

https://bugzilla.mozilla.org/show_bug.cgi?id=1738791