Add map scale info to live region

[nwisehart]

see original at: https://github.com/kellyhutchins/a11y-map/issues/10

[kellyhutchins]

more details: think information in the ScaleBar would be useful for screen reader users when they first sets focus to the map view and subsequently changes the zoom level.

We could add the text description of the ScaleBar to the aria-live region where we show the moving direction and features inside the focus square.

If we need to make the ScaleBar widget itself accessible, we will probably need a sr-only element to show the text description of the information in ScaleBar. We can then use the aria-live pattern to update the text description when the zoom level changes. There is also a new On Demand Live Regions module that claims to be more reliable than aria-live.

[Malvoz]

On Demand Live Regions

Is this referring to https://github.com/Heydon/on-demand-live-region?

[kellyhutchins]

@Malvoz we were looking at that but I can see that the repo hasn't been updated in 4 years so I don't think we'd consider using it at this point. We just need to add logic so scale info is read out