Add node.js code samples for all AutoEval docs

[saqadri]

Summary

Now that we have an AutoEval client implemented in Node (see https://github.com/lastmile-ai/lastmile-node/blob/main/src/lib/auto_eval.ts), we add code samples for Node.js usage of AutoEval to the docs.

Changelist

Added code samples for every place we have a Python code sample already.

Test Plan

Tested the code samples by running them to ensure they work as advertised.

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[saqadri]

• Add node.js code samples for all AutoEval docs #91 👈 (View in Graphite)
• main

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