Summary: Looks like this isn't being locked when it should be.
Reviewers: ricky, levi, scottg, schneider
Reviewed By: scottg, schneider
Subscribers: jenkins
Differential Revision: https://phabricator.pinadmin.com/D84952
* Added a member to `ASTextKitAttributes` that is an optional delegate to the struct's NSLayoutManager.
* Changed ASTextNode to set this delegate to an instance of ASTextNodeWordKerner.
* Updated init method of `ASTextKitContext` to take an optional NSLayoutManager delegate
* Added the files in TextKit folder to the public headers (so we can include ASTextNodeTypes.h)