Initial Vietnamese translation

[runlevel5]

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[stomar]

Thanks for your PR and the effort you already put into it, but we cannot merge it in this form.

Adding a new translation is a major step that needs some coordination. To get some idea, you could have a look at the discussion for the Russian translation that is on the way right now, see #183 and the milestones, see #214.

1. Precondition for starting a new translation is a team of coworkers (a single contributor is a too high risk for another abandoned translation in a couple of months)
2. Open an issue with the proposal for vi
3. In the issue we will discuss whether this will happen
4. and then coordinate the work and start with PRs

Already some technical details I noticed (only relevant in "stage" 4.)

• the translation will happen on a dedicated branch, not master
• please do only commit translated pages, not the English originals
• the language for commit messages is English