By David Shepardson WASHINGTON (Reuters) – China has issued visas to American investigators and technical advisers to support its investigation into last week’s deadly crash of a China Eastern Airlines Boeing 737-800 in that country, the U.S. National Transportation Safety Board said on Tuesday. “The team hopes to depart this week,” the NTSB said in a tweet. In addition to NTSB investigators, China has issued visas to technical advisers from the Federal Aviation Administration, Boeing Co. and 737-800 engine maker CFM, the NTSB said. It is still unclear whether the U.S. team will need to quaran…