ARIA Data Visualisation module

[LJWatson]

The accessible data visualisation use case keeps coming up. I wonder if it's time to revisit the idea of an ARIA Data Visualisation module?

We talked about it in the early days of the ARIA Graphics module, when the SVG A11y TF was still in existence. I don't recall now why it didn't progress, but perhaps @Shepazu, @AmeliaBr, or @Chaals will recall.

It could be argued that much can be accomplished with existing ARIA roles and attributes, but I think there are (at least) two reasons why that isn't the best solution:

1. Consistency of implementation. This is particularly important across educational materials. The last thing we'd want is for materials from one educational source to use different roles (with aria-roledescription), different navigation etc.
2. Navigation of data constructs. It's almost certain that we'll need to introduce ways of navigating constructs like Venn diagrams, scatter plots etc, or at least to have screen reader supported ways of navigating (as we do with tables for example).