By Trevor Hunnicutt WASHINGTON (Reuters) - President Joe Biden celebrated new U.S. citizens at an event at the White House on Friday, the same day his administration rolled out a government-wide strategy to encourage more immigrants to become citizens. "It's dreams of immigrants like you that built America and continued to inject new energy, new vitality, new strength," Biden said in the East Room, thanking the 21 naturalized Americans for choosing the United States as their home. "We've seen that most clearly during this pandemic, with immigrants as frontline workers and as scientists and res...