Use aria-label for 'Enable alt attribute' when 'Output SVG Inline' is enabled

Attached patch adds the aria-label attribute to inline

Re-rolled against HEAD.

Nice and smart approach. But can you point to some docs online that confirm that the aria-label attribute alone on the SVG itself is sufficient for screen readers and behaves the same way as the <title> and <desc> tags inside the SVG itself?

All I've found online here (https://css-tricks.com/accessible-svgs/) suggests that the proper accessible approach is to put the alt text as the <title> tag and then reference it from aria-labelledby attribute. And then also implementing <desc> tag, accompanied by the aria-describedby attribute.