fix(copy-button): add aria-label for the copy button

[jendowns]

Closes #3734

The originating issue identified a labeling problem with the CopyButton, and also with the CopyButton used inside the single-line and multi-line CodeSnippet variations.

• For the CopyButton, I added an aria-label. (The aria-label on the inner svg can be removed, in this case.) This removes the DAP violation for the CopyButton.

• For the single- and multi-line CodeSnippet, the fix for the CopyButton helps, plus I also made sure to include default values for the a11y-related props in those storybook demos. This removes the DAP violations identified in AVT 1 - Single line, Multi line CodeSnippet, and CopyButton has DAP violation #3734

Changelog

Changed

• use aria-label in the CopyButton
• add default values for a11y props in the CodeSnippet storybook demo

[asudoh]

LGTM 👍 - Thanks @jendowns!

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[dakahn]

I think we totally need an aria-label for this icon button and I agree the tooltip we get for title isn't up to spec (should be displayed on focus, be persistent, dismissable etc).

That said having a poorly accessible tooltip is better than none at all here I think -- if for no one else than our sighted users who expect this interaction. Can we wait to remove the title attribute and open a ticket to add our Tooltip component to CopyButton and remove title with that work?

[jendowns]

Thank you @dakahn -- that makes a lot of sense. I just restored the title attribute in my latest commit 👍

[emyarod]

looks good to me, not seeing any more DAP violations

[dakahn]

Wonderful!