Sets if this Body can be separated during collisions with other bodies.
When a body is immovable it means it won't move at all, not even to separate it from collision
overlap. If you just wish to prevent a body from being knocked around by other bodies, see
the setPushable method instead.
Optionalvalue: booleanSets if this body will be separated during collisions with other bodies. Default true.
Provides methods used for setting the immovable properties of an Arcade Physics Body.