Addition: clarify when to expose a required element as invalid

[scottaohara]

Not the happiest with my initial wording here, but figure maybe others can review and help provide some better text.

The intent here is to tell browsers to NOT expose a required field as invalid until after a user has interacted with it in some way (blur and left empty or entered an invalid value, or attempted to submit a form of required elements without filling them in).

Closes #394

related to w3c/aria#1488

and Chromium bug: https://bugs.chromium.org/p/chromium/issues/detail?id=1318969#c17

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[JAWS-test]

I think it's very good because it would finally solve this old problem. I only wonder if it is technically possible, because the HTML specification specifies something else and in my opinion the HTML specification and this specification would contradict each other.

[scottaohara]

Update:

Chromium browsers have implemented this change and now the invalid state is not announced until a user has entered an invalid value to a field.

Safari on macOS also does not announce the invalid state with an untouched field. Safari doesn't announce a field as invalid when it has an incorrect entry - there is a browser form message that appears that indicates the incorrect entry, but the field itself does not expose an aria-invalid=true.

Firefox announces an untouched required field as invalid.

[scottaohara]

thanks @cookiecrook. i pulled in your suggestion and also broke the paragraph into two parts.

[scottaohara]

this pr should pull in the work steve started in #395

edit: no, that should be its own PR still.

[scottaohara]

per the approving review and the fact the chrome bug has been marked as fixed, i'm merging this PR.