WASHINGTON — The government on Tuesday announced plans to update its safety rating system for new cars and trucks to include whether the vehicle has technology to avoid crashes, in addition to how well it protects occupants in accidents. The 5-star rating system now uses crash tests to assess how well people inside are shielded from injury or death in front, side and rollover crashes. While that will remain a big factor in the ratings, they also will take into account whether the vehicle has nine technologies that can help prevent or lessen the severity of crashes.