Link option on container blocks is not accessible

[cbirdsong]

The way EditorsKit implements the Link Toolbar option on cover, group and column blocks is by adding an empty <a href="/whatever/"></a> to the end of the container to stretch out across the entire container. This is an instant WCAG failure since there is no text inside the link for people using screen readers to tell where the link goes.

More information:

• https://dequeuniversity.com/rules/axe/4.4/link-name
• https://www.w3.org/WAI/WCAG21/Understanding/link-purpose-in-context.html
• https://www.w3.org/WAI/WCAG21/Understanding/name-role-value.html