Clarify ping_type behavior in ESM configuration

[rajatsingh47]

Summary

This PR updates the README documentation to clarify the behavior difference between ping_type = "udp" and ping_type = "socket" in the ESM configuration.

Key Updates

• Describes that udp requires both IP and port, and may silently fail in some environments.
• Explains that socket uses ICMP and is more reliable for basic node availability.
• Adds usage guidance and default behavior notes.

Testing

• Confirmed that ping_type = "udp" does not send pings if port is provided.
• ping_type = "socket" correctly sends ICMP pings at configured intervals (10s).

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