Create header file for interface declaration
<rdar://problem/124950453>
Pull request: https://github.com/WebKit/WebKit/pull/26055
Committed 276290@main (e6533346dc5a): <https://commits.webkit.org/276290@main> Reviewed commits have been landed. Closing PR #26055 and removing active labels.
Re-opened since this is blocked by bug 271192