Is your feature request related to a problem? Please describe.

The Navigation block allows us to have multiple instances of navigation on the same page, each of these wrapped in a <nav> tag. To make it easier for screen reader users to make sense of multiple navigations, each <nav> tag should have an aria-label indicating what its contents are, e.g. "Site navigation" or "Categories navigation".

It won't be easy to generate an aria-label based on the contents of the block, so we might have to depend on users adding it in as a setting.

Describe the solution you'd like

A setting in the Navigation block allowing us to add a title, or (very) short description of the purpose of that Navigation. The content of the field should then be added as aria-label on the <nav> tag.