docs: add Shiny (for Python) to "works well with" section (#9558)

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## Description of changes
Ibis works great within Shiny for Python as well, not just Quarto. Add
link to Shiny to the docs.
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## Issues closed

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docs/why.qmd

@@ -340,6 +340,7 @@ Ibis already works well with dashboarding libraries like:
 - [Streamlit](https://github.com/streamlit/streamlit)
 - [Dash](https://github.com/plotly/dash)
 - [Quarto dashboards](https://github.com/quarto-dev/quarto-cli)
+- [Shiny](https://shiny.posit.co/py/)
 
 Ibis already works well with machine learning libraries like: