docs: Add javascript version of langgraph/sql-agent (#1050)

Just translates the Python version of the langgraph sql-agent tutorial
to js.

- Depends on langchain-ai/langchainjs#9228
- See also langchain-ai/langgraphjs#1750

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Co-authored-by: Hunter Lovell <[email protected]>
Co-authored-by: Hunter Lovell <[email protected]>
Co-authored-by: Lauren Hirata Singh <[email protected]>
Co-authored-by: Christian Bromann <[email protected]>

Author: 4 people