Add FunctionComponent matcher

[krnlde]

I'd like to use snappify in a hook-based environment where FunctionComponents are key. Unfortunately there is yet no matcher for those. I propose change to also catch FunctionComponents.

TBD: Should SFCs also be supported?

[denisraslov]

Hi @krnlde!

Thank you for the PR! Yes, I think it's a great idea to add matchers for FunctionComponent, SFC and even FC.
It would be great if you could also add matchers for SFC and FC and some tests to cover the new matchers to this PR (you can find the tests in __tests__/componentReader). I would be happy to merge these changes!

[krnlde]

Nice :) Will do!

[krnlde]

I added SFC and FC but tbh I don't understand how to write your componentReader tests :D any support on this? Create new files or extend existing ones?