Draft: Initial draft of the Kirigami.ContextMenu API
TextField isn't very customizable in terms of it's context menu, and both of our QQC2 styles inject their own context menu because Qt believes it's not important enough. This context menu, while nice, doesn't allow applications to inject their own items. This is a new API that can be used by qqc2-breeze-style and qqc2-desktop-style. I don't know a better place to put this unfortunately, but Breeze and Desktop styles both depend on Kirigami.
This is still a big TODO, and I'm currently working on a real use-case to really flesh out the API. This also needs to be rebased onto KF6.