docs(channels): add Channels feature documentation

- Add overview page explaining channels architecture and configuration
- Add Telegram channel setup guide with bot creation steps
- Add navigation entries for channels section

This documents the new Channels feature that allows users to interact
with Qwen Code agents from messaging platforms like Telegram.

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

docs/users/features/_meta.ts

@@ -13,4 +13,5 @@ export default {
   'token-caching': 'Token Caching',
   sandbox: 'Sandboxing',
   language: 'i18n',
+  channels: 'Channels',
 };