Change Traditional Chinese (zh-TW) icon to the Taiwan flag

Problem: The current icon for Traditional Chinese is not the Taiwan flag, which confuses.

Request: Map zh-TW to the Taiwan flag; map zh-HK, zh-MO, zh-CN to their respective flags. Use locale-based mapping instead of “Traditional/Simplified” text.

Selecting zh-TW displays the Taiwan flag with “Traditional Chinese (Taiwan),” which is consistent across platforms and readable by screen readers.