docs: add v1.2.0 new features documentation (#808)

- Add TG_ALLOW_USER_LANG variable to worker-vars.md (zh/en)
- Add SUBDOMAIN_FORWARD_ADDRESS_LIST with sourcePatterns docs (zh/en)
- Add /lang command and language switching docs to telegram.md (zh/en)
- Add TG_ALLOW_USER_LANG example to wrangler.toml.template

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

vitepress-docs/docs/en/guide/feature/telegram.md

@@ -36,6 +36,25 @@ pnpm wrangler secret put TELEGRAM_BOT_TOKEN
 
 ![telegram](/feature/telegram.png)
 
+## Language Switching
+
+> [!NOTE]
+> This feature is available since v1.2.0
+
+Telegram Bot supports Chinese and English switching. Users can set their language preference via the `/lang` command.
+
+### Enable Language Switching
+
+You need to configure `TG_ALLOW_USER_LANG = true` in worker variables to enable this feature.
+
+### Usage
+
+- `/lang zh` - Switch to Chinese
+- `/lang en` - Switch to English
+- `/lang` - View current language setting
+
+Language preferences are saved to KV, and each user can set their preference independently.
+
 ## Mini App
 
 Can be deployed via command line or UI interface