Explainer on relationship between mediaSession and audioSession

[lucas42]

Given the naming of mediaSession and audioSession, I think it would be useful for their explainers to mention each other and explain the differences.

For people familiar with older web standards, but approaching these two for the first time, the naming can be quite confusing.
For example, HTMLAudioElement and HTMLVideoElement both inherit from HTMLMediaElement. So newcomers may assume that audioSession inherits from mediaSession in a similar fashion. But it appears that quite reasonable assumption is incorrect.

If these newer APIs are going to deviate from long-standing convention, then it would be useful for explainers to draw attention to that fact explicitly.