Babel plugin should only do transformations when emotion is imported

[DingoEatingFuzz]

• emotion version: 9.1.1

Problem description:

The babel plugin injects parameters to any function call for a function with the name css. This generally works, but it's possible to have a function named css that isn't emotion's css. In this case, the results are very unexpected.

I ran into it using the Webpack Blocks library, which uses css as a function shorthand for the webpack css loader.

Suggested solution:

Before doing any code transformations, check to see if emotion is even imported. This is still naive since variable shadowing could make css in a function scope still not be emotion's css despite emotion's css being imported, but it's an improvement.

[cameron-martin]

Duplicate of #344

[stale]

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