Implement hitstun and knockback.

src/game_settings.rs

@@ -11,6 +11,10 @@ pub struct FighterSettingsCommon {
     pub walk_speed_ease: FGi32,
     pub ground_max_horizontal_velocity: FGi32,
     pub ground_friction_over_walk_speed_multiplier: FGi32,
+    pub knockback_stacking_window: u32,
+    pub knockback_decay_per_frame: FGi32,
+    pub knockback_launch_velocity_multiplier: FGi32,
+    pub hitstun_frames_per_unit_knockback: FGi32,
 }
 #[derive(Reflect, Serialize, Deserialize, Clone)]
 #[reflect(opaque)]