Extract fixedmat4 into its own separate module.

src/fighter/baked_animation/asset_baking.rs

@@ -1,8 +1,8 @@
 use super::{
     BAKED_ANIMATION_FPS,
-    fixed_transform::FixedMat4,
     runtime::{BakedAnimationClip, BakedFighterAnimations},
 };
+use crate::math::fixed_transform::FixedMat4;
 use crate::fighter::{animation::AnimKind, manifest::FighterManifest};
 use bevy::{
     asset::{