Both Adrian Roselli and Scott O'Hara recommended a component that manages a single live region.
The `live-region` would then expose APIs to allow append/remove content as needed. The SR need only monitor one live region and need not make up its own rules about how to handle competing regions.
The live region has `aria-atomic` set to `false` to only read out the content that's changed
The live region has `aria-relevent` set to the default `additions text` to read out only when nodes and text content is added to the region.