addToWorld method
Add the vehicle including its constraints to the world.
Implementation
void addToWorld(World world) {
for (final key in particleBodies.keys) {
world.addBody(particleBodies[key]!);
}
for (int i = 0; i < constraints.length; i++) {
world.addConstraint(constraints[i]);
}
//world.addEventListener('preStep', _update);
}