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/channels/_meta.ts

@@ -0,0 +1,4 @@
+export default {
+  overview: 'Overview',
+  telegram: 'Telegram',
+};