Placeholder sounds (issue #124)

[SenhorFlibble]

Placeholder sounds from Freed∞M (2020 repository) and Blasphemer (2017 repository) for Boss 1, Boss 2, Death Knight, Ogre, Shambler, Zombie + a few more sound effects. I tried to pick effects that would sound more or less like their original counterparts, or at least not be completely out of place when they're played.