List View: consider showing heading level and ensure aria label shows heading level

[annezazu]

This came up as part of the Hallway Hangout on improving accessibility in the Site Editor when discussing the advantages and pain points of List View. You can explore this discussion starting at 48:36 to 49:45. In this case, the proposal is to add clearly in List View, the heading level and ensure the area label is reflected. This aligns nicely with additional functionality like showing image previews in List View: #53381.

This is a poor, hacked screenshot but here's a visual:

[joedolson]

I'm not sure this needs a lot of accessibility feedback: this would be a significant enhancement for understanding the content hierarchy of the page, which otherwise doesn't have visibility in most views.

Just make sure that the visible indicator is reflected for screen readers, as well.

[annezazu]

Sweet :) removing the needs feedback label.