docs: New chapter - low level servers, 3.10

[softchris]

A new chapter on low level servers in MCP

Should cover why use it

• you have more control over architecture
• or Python, you can use context managers

Should include

• example of a server using it, use SSE or streaming http (doesn't work properly with stdio)
• should show how to handle listTools and callTools and how to architect your tools in a tools folders

See 3.1 for chapter structure, https://github.com/microsoft/mcp-for-beginners/tree/main/03-GettingStarted/01-first-server

[softchris]

@glaucia86 see description above, thanks for helping out with this :)