docs: integration with marimo guide (#13691)
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## Summary
This change adds a new integration guide, on using uv with marimo
notebooks. It is similar to but simpler than the existing Jupyter guide,
since marimo stores notebooks as Python files and also integrates
tightly with uv for package management.
The guide showcases four ways of using uv with marimo:
1. marimo as a standalone tool (`uvx`)
2. managing inline script metadata (an alternative to Jupyter kernels,
marimo has no concept of kernels)
3. in project environments
4. in non-project environments
## Test Plan
N/A as this is a docs-only change.
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Co-authored-by: Zanie Blue <contact@zanie.dev>
