add audio.rs; publish to lib.rs

[ekalosak]

This compiles but is not tested; I'm putting this PR up early to get feedback ASAP from library maintainers.

Plan now is to:

1. Make a CLI binding, user-like test
2. Unit test

but I don't have a ton of time for this proj, I'm sorry to say - so perhaps someone else will get this over the line.

[AlbertMarashi]

The use of unwraps which might result in panics is not ideal so I think those should be propagated in the result errors.

Can you write some tests to validate the code as well?