feat(td-headers-attr): report headers attribute referencing other <td> elements as unsupported

[engineerklimov]

Fix for the header attribute check. The check will report cells that references other <td> elements. Added unit and integrations tests as requested in corresponding issue.

Closes: #3987

[engineerklimov]

Please, let me know if there are any changes needed. Thanks!
@WilcoFiers and @straker for vis.

[WilcoFiers]

@engineerklimov Heyya, apologies about the delays. Lots to do. I'll try to get to it within the week.

[engineerklimov]

Appreciate your response, Sir
Looking forward to the review

[WilcoFiers]

There are some scenarios the original ticket didn't consider that I feel we need to test before we can start failing this. Let me know if you have the necessary software to do this testing, otherwise we'll see what we can do on our end. At the very least we'll need to test this with NVDA + Firefox and JAWS + Chrome. Normally we'd also want VO + Safari but since it doesn't support the headers attribute anyway there's no point in that.

[WilcoFiers]

I'm going to change this PR title to "feat". This PR makes the rule stricter, we can't put that in a patch release.

[engineerklimov]

@WilcoFiers I did all changes, the only thing left is locales updates. Can you check error messages? If they are fine i will update all translations.

[WilcoFiers]

LGTM. Let me ask a colleague for a final OK, since I wrote part of the solve.

[dbjorge]

Thanks for the contribution! This is looking good overall, just noticed a few more bits to clean up

[engineerklimov]

I tried to update locales. I found that all locales are quite outdated. Not sure that this change is good place to bring all locales up to date. So i updated only "ru" which i contributed recently. Not sure what is contribution policy here.

[dbjorge]

It looks like fmt_check is still showing 1 error to resolve, + it'd be good to do an npm run build to re-generate /locales/_template.json to match the most recent rule text update.

Other than those, this looks good to me!

[engineerklimov]

It looks like fmt_check is still showing 1 error to resolve, + it'd be good to do an npm run build to re-generate /locales/_template.json to match the most recent rule text update.

Other than those, this looks good to me!

I did updates you requested, there is problem with @WilcoFiers test case with wrong closing tag. Prettier shows error here somehow line ignore not working.

So i updated .prettierignore, let me know if there is better way to fix it.

[dbjorge]

So i updated .prettierignore, let me know if there is better way to fix it.

I'm pretty sure this was just a typo in his suggestion; this is intended to be a case exercising that the rule correctly fails if a headers attribute. points to a th element with a non-heading role, so I think it's correct for it to just be a th element. Shouldn't need to add it to .prettierignore, this is just prettier correctly catching a typo.

Suggested change

	<th role="cell" id="th-role-cell-hdr">Hello</td>
	<th role="cell" id="th-role-cell-hdr">Hello</th>