Incompatible with React's strict mode

[stephenmathieson]

@axe-core/react is not compatible with React's Strict Mode. Wrapping an application with <React.StrictMode> while using @axe-core/react produces tons of errors about its usage of findDOMNode.

It would be great if I could develop my app using Strict Mode and have accessibility checks running at the same time.

[mtsknn]

👍 Probably a duplicate of #94.