Add Traditional Chinese language entry

[hezhen0816]

This adds Traditional Chinese to the supported language list so the existing zh_TW translation can appear in the language selector.

The zh_TW translation files were added in #9705, and this follows up on the maintainer note that the language entry would be added later.

Testing:

• Not run locally; macOS build is currently blocked by local dependency build issues unrelated to this one-line language entry change.

[Copilot]

Pull request overview

Adds Traditional Chinese to the app’s supported language whitelist so the existing zh_TW translation catalog can be surfaced in the language selector and accepted as a configured/system language.

Changes:

• Add wxLANGUAGE_CHINESE_TRADITIONAL to s_supported_languages.

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[Copilot]

Adding Traditional Chinese here will allow the zh_TW catalog to pass the supported-language filter, but the Preferences language combobox currently overrides several languages (including Simplified Chinese) to show a native self-name. Without adding a similar override for Traditional Chinese, the new entry will likely display as the wxWidgets default description (e.g., "Chinese (Traditional)") and be inconsistent with the existing Chinese entry. Consider adding a Traditional Chinese display-name override in PreferencesDialog::create_item_language_combobox when comparing against wxLocale::GetLanguageInfo(wxLANGUAGE_CHINESE_TRADITIONAL).