Add Game End Placements

[rapito]

Game End Placements

• Reads Placements from slp files based on this SPEC update.

Changes

• Add PlacementType to GameEnd
• Add GetWinners method to lib
• Add specs

See Readme.md changes for a better description.

Dependencies / Related PRs

• https://github.com/project-slippi/slippi-wiki/pull/31
• https://github.com/project-slippi/slippi-ssbm-asm/pull/94
• https://github.com/project-slippi/Ishiiruka/pull/349

[NickCondron]

Player placements does not reflect differences in damage based on my testing. I think stats should check damage at the end of the game too.