Preserve existing options passed to styled calls

[Andarist]

fixes #582

What:

Preserving existing options passed to styled calls when using emotion's babel plugin

Why:

It would ease creating custom emotion wrappers.

How:

Checklist:

• Documentation
• Tests
• Code complete

TODO:

• fix flow typings - I'd appreciate help with this, dunno why they are not compatible atm
• handle more cases (like buildStyledObjectCallExpression)
• decide what about rest of the arguments, they are lost at the moment too, should we preserve them?

[emmatown]

Let's preserve the rest of the arguments and for the flow errors, just add // $FlowFixMe comments for now.

[Andarist]

So I think this is code-complete, you can make a code review of this. I'd appreciate hints on how to fix those flow types, I always struggle with a little bit more complicated cases :s

[codecov]

Codecov Report

Merging #584 into master will decrease coverage by 0.06%.
The diff coverage is 95%.

Impacted Files	Coverage Δ
packages/babel-plugin-emotion/src/macro-styled.js	100% <ø> (ø)	⬆️
packages/babel-plugin-emotion/src/index.js	96.69% <95%> (-0.23%)	⬇️

[emmatown]

Looks good 👍 Typing this well with flow is hard since flow doesn't know how the isSomeNodeTypeHere stuff works and etc. It's basically more effort than it's worth, we just use flow here for more basic stuff, i.e. functions are called with the correct number of arguments, things that are being imported actually exist and etc.