Add Vietnamese language support

[amazingnerd]

Font Name (Geist Sans/Geist Mono):

• Geist Sans

Description of the Issue:
It has not supported Vietnamese language yet.

Steps to Reproduce:

1. Add Vietnamese language support.

[hiepxanh]

#144 PR here, not understand why they not merge

[janbrasna]

Because the PR can't be merged now without resolving conflicts, unfortunately.

(And it probably includes formatting changes even to all the other glyphs, so will need a thorough review regarding impact.)

But is a wonderful piece of work anyway. Hopefully it will get some attention soon, and perhaps maintainers will help clear the conflicts and remove any superfluous changes to move it forward.)

[guidoferreyra]

This is in progress! It will be available in the repo in the next few weeks :)