* Add Vietnamese localization file for OrcaSlicer
* add Vietnamese po file
* Add Vietnamese language support in GUI (#11000)
- Added Vietnamese (vi_VN) to the language mapping in GUI_App.cpp.
- Updated Preferences.cpp to include Vietnamese in the language combobox and display its name in Vietnamese (Tiếng Việt).
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Co-authored-by: SoftFever <softfeverever@gmail.com>