Easy implementation of Google reCAPTCHA

[CHadetz]

Maybe address this when/if refactoring?

[k1sul1]

Not that I've tested it, but it should be possible now using ReactDOM.createPortal. Pass an useRef() reference to the component properties to override the built-in ref, and use that ref to inject in another component that will do the recaptcha stuff. Backend implementation should be similar as in older versions of WPLF.

edit; #7