We should be able to choose our preferred export format

## Current Behaviour
The type of export for audio is selected automatically based on the import type (I believe)

## Expected Behaviour
- [ ] In the 3rd step of the export wizard, we should have a dropdown with the type of formats we can export to (eg. .wav, .m4a, webm, etc.)
- [ ] The type selected will apply to all the exported audio items