A new video posted today on Vietnamese site tinhte.vn (via 9to5Mac) demonstrates what appears to be an official Apple Lightning to 3.5mm headphone adapter that will likely ship with the new iPhone coming this fall. The adapter, which features a design reminiscent of Apple’s previous Lightning accessory adapters, appears to be between 2.5” and 3” in length and includes a male Lightning connector on one end and a female 3.5mm headphone…