Function spawn_particles 

pub fn spawn_particles(
    commands: Commands<'_, '_>,
    pool: ResMut<'_, ParticlePool>,
    meshes: ResMut<'_, Assets<Mesh>>,
    materials: ResMut<'_, Assets<ColorMaterial>>,
    visualization_mode: Res<'_, VisualizationMode>,
    config: Res<'_, SPHConfig>,
)