feat: Add Mandarin Chinese locale support

[O2sa]

Mandarin Chinese is the most widely spoken language in the world with over 1 billion native and non-native speakers. Adding Mandarin Chinese locale support will make the application accessible to a vast community of Chinese-speaking developers.

Overview

Mandarin Chinese (Simplified) will be added as a new supported locale with the language code zh. Chinese uses left-to-right (LTR) layout, making this a straightforward addition similar to French and Spanish.

Tasks

• Create a new locale file locales/zh.json with all translation keys from locales/en.json translated to Mandarin Chinese (Simplified).
• Update lib/i18n-core.ts to add zh to the supportedLocales array.
• Add Mandarin Chinese entry to the localeMeta object in lib/i18n-core.ts with the following configuration:

  zh: { dir: "ltr", label: "中文" }

• Test the language switcher to ensure Mandarin Chinese appears in the dropdown menu.
• Test the application with Mandarin Chinese locale selected to ensure all UI elements display correctly.
• Verify that all text content renders properly without layout issues.
• Ensure proper character encoding (UTF-8) is maintained throughout the application.
• Update CONTRIBUTING.md with instructions for translating content to Mandarin Chinese (if not already documented in the localization guide).

Translation Keys

All translation keys from the existing English locale must be translated to Mandarin Chinese (Simplified). The keys include:

• Application titles and subtitles
• Error messages
• UI labels and buttons
• Explanations and descriptions
• Comparison metrics
• Community contribution labels
• And more (reference locales/en.json for the complete list)

Testing

• Language switcher displays "中文" correctly.
• All pages render without errors when Mandarin Chinese is selected.
• No layout shifts or broken styling in LTR mode.
• All Chinese characters display correctly without encoding issues.
• All Mandarin Chinese translations are grammatically correct and contextually appropriate.

Tip

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