Sound effects for the Hub

Solves (without music) #46 (closed). It includes sounds for hard-coded entries as listed in https://openmw.readthedocs.io/en/latest/reference/modding/sound-effects.html

The set of sounds is reasonably complete but a particular sound file can be used for multiple sound records. There's around 130 separate sound records and it's just too much to do in one go. Shared sounds do a good enough job for now.

.wav files are 16-bit at 48,000 Hz

I still need to list authors of all audio sources I've used. They are all CC0 Public Domain, but it's nice to credit people.