Refine chart aria-label

[mmazanec22]

Currently, one can set the chartTitle to add a meaningful aria-label to the visualization layer. It would be awesome if a dev could alternately set aria-label on their OrdinalFrame (or whatever) element if they wish to use their own separate title element.

Another possibility could be to make the visualization layer g element aria-label describe the type of visualization (pie, bar, etc) and then use aria-describedby if a chart title is present.