Improve audio file selection for the playlist

[jeffpaul]

Is your enhancement related to a problem? Please describe.
From @dkotter in #6:

You can currently select multiple audio files but you have to do the command+click or shift+click, otherwise it deselects whatever you have. There is an audio playlist media modal but as far as I can tell, that is not supported yet in the mediaPlaceholder component (you can get to this flow using the Classic block). This may be as good as it gets until support is added for that

Describe the solution you'd like
Review the work in #6, the current state of the develop branch, and what approach should (if any) be taken to resolve this issue. This may require some upstream work in Gutenberg to enable further progress on this issue.

Designs

Describe alternatives you've considered

Additional context