Simply get close to a vehicle and press G to enter in the passenger seat.
Just like a regular car jacking, if somebody was already in the seat and you pull them out,
they will probably come back at you ready to fight. Sometimes the cops will want to come after
you for getting into the car, so I included a clear wanted level script that automatically clears
any wanted level you might get within seven seconds of stealing the car. Also, you can't enter
locked vehicles like police cars.
I'm planning on adding the ability to enter cop cars - probably tomorrow