Add audiobook formats to publication types for books and chapters

[rupertgatti]

Is your feature request related to a problem? Please describe.
Request via OBP to publish audio recordings of book chapters

Describe the solution you'd like
Add audiobook formats to publication types for chapters and books
I don't believe there is any need to change the datamodel for digital editions to enable this.

Additional context
Most popular audiobook formats are MP3 and WAV.

[ja573]

Note to myself: after the new publication types are added to Thoth, we'll need to check if any additional work is needed on the website to implement this (doubt it)