Link Form Field: Ability to "sticky" post in list

[AlexGStapleton]

We should add a parameter to the link form field that will allow developers to sticky posts to the returned posts list. This post should be included regardless of other parameters (ie. ignore the post type, etc).

An example use case for this is the SiteOrigin Image widget. For lightbox type plugins, typically the user will need to link the image to the full sized image. Normally, they'll need to work out the link and then manually set the link via the link form field. With the ability to sticky posts and with the help of state emitters, the widget could automate this process by automatically working out the URL and showing it in the posts list.