Clarify the example in docs/intro web page

[deanja]

As a beginner I found this page confusing https://dlthub.com/docs/intro . The example could be clearer while still being brief and informal. For example, it mentions duckdb dependency only after asking the user to run the code, which for most users will fail on that missing dependency.

I'm a first time contributor. I have forked and branched the repo and edited intro.md. If you'd like to assign me this issue I will submit a PR.

[adrianbr]

thank you very much @deanja !