Help, Vietnamese Translation version

Hi, Alex.

Can you help me add translation for Vietnamese language into the plugin?
I am providing you the singular and plural translations of the needed strings.

year: N?m (singular) N?m (plural)
month: Tháng (singular) Tháng (plural)
week: Tu?n (singular) Tu?n (plural)
day: Ngày (singular) Ngày (plural)
hour: Gi? (singular) Gi? (plural)
minute: Phút (singular) Phút (plural)
second: Giay (singular) Giay (plural)

Thank you for help.