Change target to currentTarget in documentation for React forms

[huy-nguyen]

Because currentTarget is more appropriate
(https://developer.mozilla.org/en-US/docs/Web/API/Event/currentTarget)
and it makes TypeScript typing works better
(DefinitelyTyped/DefinitelyTyped#12239 and
DefinitelyTyped/DefinitelyTyped#11508 (comment))

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[aweary]

Thanks for the PR @huy-nguyen! Can you share an example where using event.target for a text element (input, textarea) is incorrect? I understand using event.currentTarget in situations like the one described in DefinitelyTyped/DefinitelyTyped#11508 (comment) but in the case of inputs there are no child elements from which the event could originate.

It may also be worth nothing that currentTarget will change if you are listening during the capture phase, making it the wrong choice in some specific situations.

[huy-nguyen]

Hi @aweary. Actually using target hasn't caused a problem for me. I just thought I'd suggest this change because it seems more appropriate and works better with the React's TS definition. I've never used an event listener in the capture phase before so I haven't thought of that use case.

[gaearon]

I'd like to leave it as is. Otherwise we'll keep getting PRs changing it back to target because currentTarget is not necessary here 😄 . If there's a problem with TS definition, please help fix it upstream. Thanks for the PR though!