Merge into testing libraries and recommend over fireEvent

Now that this package is mentioned in the testing library docs, it would be nice to expand it enough to be recommended over fireEvent in most cases and include it in the original packages. We should think about what common user interactions are missing that are tricky to implement with fireEvent. Other testing tools like Cypress could be good inspiration.

[kentcdodds]

Ok, after thinking about this and feeling revitalized thanks to @nickmccurdy’s personal interest, I’m motivated to making this happen. Let’s make this happen, and in the next day or two. We can leave this package without a major version bump (though perhaps we’d do a major version bump akin to https://npm.im/dom-testing-library to announce the deprecation of the package), and we can do a minor version bump to DOM Testing Library when we add the feature.

I’ll be working on this for the next day or two. FYI @testing-library/all-maintainers

[Belco90]

To be honest, the way user-event handles the events is how I expected testing-library to handle them the first time I use it. I think this is a good idea.