Add water footstep splashes and reduce lake wave amplitude

- Play WaterFootstep splash sounds when wading in shallow water
- Spawn foot splash particles at water surface on each water footstep
- Reduce inland water wave amplitude from 0.18 to 0.08 for calmer lakes

include/rendering/swim_effects.hpp

@@ -24,6 +24,7 @@ public:
     void update(const Camera& camera, const CameraController& cc,
                 const WaterRenderer& water, float deltaTime);
     void render(VkCommandBuffer cmd, VkDescriptorSet perFrameSet);
+    void spawnFootSplash(const glm::vec3& footPos, float waterH);
 
 private:
     struct Particle {