Implement market depth websocket subscription

[jacog2]

PAID Ticket rules

Price: 10$

README source

• Section: Socket API / Market Data
• Feature: - [ ] Subscribe Market Depth Data

Description
Add market websocket support for depth data subscriptions and emitted events.

Acceptance criteria

• Endpoint, stream event, or subscription class is described for this feature
• The appropriate client service or socket API exposes the feature
• The feature is exported where consumers need public access
• Unit tests cover request shape, service/socket dispatch, or event parsing as applicable
• README feature status is updated when implementation is complete

Created from #26 to track currently unchecked README functionality.

[zaixincheng174-ai]

/attempt #91

I will add typed market depth websocket subscription support, expose a dedicated stream subject and helper method, cover subscription dispatch/event parsing, export the public types, and update the README status.

[letronghoangminh]

Implemented in PR #111: #111

[zaixincheng174-ai]

Implemented in PR #109: #109