Table Block: add caption support

[fienen]

Describe the bug
When creating a table block, you have to manually edit the HTML if you want to include a caption on the table. A <caption> is allowed to be the first child of a <table> element for accessibility purposes as described in https://www.w3.org/WAI/tutorials/tables/caption-summary/ and https://developer.mozilla.org/en-US/docs/Web/HTML/Element/caption

To Reproduce
Steps to reproduce the behavior:

1. Create or edit a post
2. Insert a table block
3. Convert to HTML editing
4. Add a <caption> element just inside the <table> element
5. Convert back to visual editing

Expected behavior
This should not produce an error, and should be treated as acceptable markup. Bonus points if the table block editor straight up supported captions, as well as thead/tfoot without having to manually editing the HTML of the table.

Screenshots

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Chrome
• Version: 70

Additional context

• Gutenberg 4.2.0

[ellatrix]

Right, there is currently no caption support.

[Rik44444]

this issue has been closed, but in my Wordpress version 5.5 i do not have caption support in the Table block, is that correct? Or have i missed it?

[michaelmcpeekbrenau]

One year later and the Tables block still doesn't support captions and doesn't use ARIA labels to connect figcaptions with tables, either.

[talldan]

Table blocks should support captions since WordPress 5.4:

@michaelmcpeek The implementation does use a figcaption, but screenreaders should still announce this.

An implementation using the table <caption> element was attempted initially, but unfortunately browsers/assistive technologies didn't seem to support a contenteditable caption element. That might have changed now, so it could be worth looking at again.

#24205 discusses changing the caption implementation (and aria labels aren't the right way to connect a caption to a table).

[betagoo]

figcaption is not semantic. It's very big problem.