make bodyContains() handle possibly nested shadow root's

[spez]

Description

make bodyContains() handle the case where elt might be inside nested shadow dom's

Testing

Tested manually with and without nested shadow dom's

Checklist

• I have read the contribution guidelines
• I have targeted this PR against the correct branch (master for website changes, dev for
  source changes)
• This is either a bugfix, a documentation update, or a new feature that has been explicitly
  approved via an issue
• I ran the test suite locally (npm run test) and verified that it succeeded

[1cg]

no opinion on this @kgscialdone do you have one?

Definitely needs tests if it is to be accepted though.

[kgscialdone]

This is... acceptable. Recursive checks like this are gross but there isn't really a better way.