By Martin Quin Pollard WUZHOU, China (Reuters) -Chinese emergency workers found on Wednesday one of two black boxes from a China Eastern Airlines plane that crashed this week with 132 people onboard, and the United States said its investigators had been invited to the crash site. The black box device recovered is the plane’s cockpit voice recorder, based on an early assessment, a Civil Aviation Administration of China (CAAC) official told a media briefing, adding that the recording material appeared to have survived impact in relatively good shape. Flight MU5735 was en route from the southwest…