docs: add error handling when it fails to start HTTP server

[formulahendry]

Motivation and Context

In sample code of Streamable HTTP, it may fail to start HTTP server in some cases. e.g. Port 3000 is already in use.
So, add error handling when it fails to start HTTP server

How Has This Been Tested?

Test code in my Code Runner MCP Server: https://github.com/formulahendry/mcp-server-code-runner/blob/main/src/streamableHttp.ts

Breaking Changes

No

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context