Noting that there's a Time to Read Block in core that we can mimic for this Time to Listen Block: https://wordpress.com/support/wordpress-editor/blocks/time-to-read-block/

In chatting with @cedarstay, one option discussed was instead of crafting this as its own block would be to add a toggle to the podcast block to render this info around that block. See #191 for potential designs for how that could look; options there being rendering above or below the audio player as well as having the label be Duration, Runtime, Time to Listen, or some other sensible copy.