CKTextKitEntityAttributeName feature appears to be left incomplete #253

Hi all,

I'm currently trying to use CKTextComponent to attach a URL to a link as one might with NSLinkAttributeName. I saw CKTextKitEntityAttributeName, which appears to allow the attachment of an arbitrary object to a range in the string. So far so good, I can attach my NSURL here.

CKTextComponentViewControlTracker detects and creates a CKTextKitTextCheckingResult with my URL attached. However, the text checking result only appears to be used to track highlighting, and the actual -entityAttribute property is never accessed.

Therefore, this feature appears to be incomplete or disabled, so reporting if this if unexpected. It doesn't seem to be much work to use CKComponentActionSend() somewhere like -continueTrackingForTextComponentView:... in order to dispatch an event with my -entityAttribute. However, I'm afraid I'm unlikely to have the time. I would certainly be interested in getting some input on this, though.

Also, the need to set layer attribute with ck_setAllowsHighlightDrawing: on the highlightable component was very easy to miss, so could do with some documentation there 😬