Rename songs array to audio array in Config

[danpastori]

Discussed in #503

^{Originally posted by danpastori May 4, 2022}

👉 Describe the problem

Right now you add audio to the AmplitudeJS configuration through a songs array. This doesn't make sense if you are working with audio files that aren't songs such as podcasts.

👥 Problem evidence & reach

Any user that works with podcasts, interviews, etc.

🥰 Describe the "impact" on users?

It's more developer friendly to name the songs array as audio if the user is working with audio files that aren't songs (i.e podcasts).

🏆 How to solve this problem

Rename the songs array to audio and update all references within the code. This will be a breaking change from 5.3 -> 6.0 but will document it.

💯 How do we validate the problem is solved?

Users can semantically set audio instead of songs within AmplitudeJS making it more inline with their use case.