chore(i18n): Add Vietnamese translations

[vodquang96]

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[pennersr]

There a quite some translations that are still to go. Can you look into those?

[vodquang96]

That's the plan. Not sure if I have time for that now. Do you mind keeping this pr here until I'm done?

[coveralls]

coverage: 95.796%. remained the same
when pulling bd536ed on vodquang96:add-vi-locale
into b0ae821 on pennersr:main.