_WKHitTestResult should expose a linkDataMIMEType property
<rdar://119404077>
Pull request: https://github.com/WebKit/WebKit/pull/22319
Committed 272600@main (00a7a1e70c1a): <https://commits.webkit.org/272600@main> Reviewed commits have been landed. Closing PR #22319 and removing active labels.