dillon1000/react

[Fresh] Initial Babel plugin implementation (#15711)

* Add initial Babel plugin implementation

* Register exported functions

* Fix missing declarations

Always declare them at the bottom and rely on hoisting.

* Remove unused code

* Don't pass filename to tests

I've decided for now that the plugin doesn't need filename, and it will be handled by module runtime integration instead.

* Fix bugs

* Coalesce variable declarations