Support for 4 bit wav file import/export

[Hundredlegger]

I think this feature will be useful, espescially since there are many chips that have 4 bit PCM support. Since 4 bit unsigned wavs are a thing, why not implement this feature?

I hope this suggestion can be useful someday.

[BTTFdude]

I second this request. Also for 4-bit sound importing, there should be an option to choose either low nibble first or high nibble first, since many games are different in how they use 4-bit PCM.