Moving audio assets

[Outvi V]

Currently the repo's size is 49MB (see this) and most of it is the history of audio assets, which might be a problem on cloning or source management. We might use one of the following options to handle this:

1. Move audio to another repository
2. Move audio to a object storage

Suggestions are welcomed.

[Outvi V]

suisei-cn/sbtn-assets@d5912ed88