Add tests

[bloodyowl]

#563

[rickyvetter]

This looks awesome! Can we see the GH actions/tests run on this PR? Or does it need to land first?

Only question/concern I have is BS version bump. We will bump to 7.3 soon regardless but it's a very new release and I'd like to give a bit of time for organic upgrade before pushing people.

[bloodyowl]

@rickyvetter I think it needs to land on master (or at least in the correct repository) in order for the action to run.

The BS version bump is so that reason-test-framework can have simpler bindings (using unit instead of an undefined value for function return values, which is significant in Jest). I'll release a version tomorrow that adds that back so that the bump isn't necessary.

[bloodyowl]

@rickyvetter Here's how it looks on the reason-test-framework repo:

[bloodyowl]

I'll add a few more tests later today:

• React.null
• React.string
• React.int
• React.float
• React.array
• React.cloneElement
• Ref
• Children
• Context
• useReducerWithMapState
• useLayoutEffect
• Basic event support