Add support for [AtomString] with USVString type in our WebIDL bindings. This is needed to mark the AtomString(const String&) constructor explicit.
Pull request: https://github.com/WebKit/WebKit/pull/370
Committed r293301 (249926@main): <https://commits.webkit.org/249926@main> Reviewed commits have been landed. Closing PR #370 and removing active labels.
<rdar://problem/92226128>