write SIMD version for game_engine::math

[TrueDoctor]

write versions of Mat2, Mat3, Vec2, Vec3 using SIMD operations from the packed_simd crate

[konsumlamm]

Currently the normal versions are used (mainly because they're guaranteed to not be platform dependant). SIMD versions of Mat2 and Vec2 are WIP but currently not in use. The source code will remain in the crate until we decide to use it for optimizations (even though this is unlikely to be needed) or drop it.