Functional components data merging util

[miljan-aleksic]

What problem does this feature solve?

Hi! Components have the extend feature, but there is nothing similar for functional components. The problem and the solution is well explained at https://github.com/alexsasharegan/vue-functional-data-merge and while that works fine and I am very grateful to the author, I would like to request an official in core solution.

Why? Because there are edge situations or new features that 3rd party solutions will have a difficult time to be on top.

What does the proposed API look like?

Similar as done by @alexsasharegan

[wxsms]

+1 I thinks this is necessary for all users of functional components. Otherwise it can hardly work as expect.