Docs: Fixed incorrect WebSocket example in README

[pugud]

Description

This PR updates the WebSocket example code in the README for both public and private channels.

Changes

• Updated the public WebSocket example to use Connect() followed by SendSubscription(...) with proper error handling.
• Updated the private WebSocket example similarly for the "order" topic.
• Improved clarity and correctness of the usage example.

Reason

The previous examples used Connect() with a direct parameter, which is no longer correct or supported by the SDK. This update reflects the correct usage pattern with subscription and error handling.

Checklist

• Updated README examples
• Verified the new example code compiles and runs as expected
• (Optional) Add a test or snippet if needed