New comment by Johnnynator on void-packages repository

https://github.com/void-linux/void-packages/pull/20454#issuecomment-607233036

Comment:
I missed the soundtrack license. (`./hyperrogue-music.txt`)
```
HyperRogue soundtrack under the Creative Commons BY-SA 3.0 license, http://creativecommons.org/licenses/by-sa/3.0/
```