Added an LLM-based ETL example that adds the website for a given company.

[Etherdrake]

I created this tidy little program that takes in data about a company and tries to find the website (without web-search, this could make it far more effective). This example has been slimmed down to add just the company name where one request is made per company. I figured it would be cool to add it as an example.

I also added the missing documentation about how to install langchaingo 😉.

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