[Docs]: Add missing examples

[schloerke]

First seen when looking at https://github.com/posit-dev/py-shiny/actions/runs/21910249650/job/63261778410?pr=2163

When building the website, the annotations gave 10 warnings about missing examples. We should turn the warning into an error and either:

• acknowledge the missing the example
• make an example

Test with make docs-quartodoc

Upgrade to error near here:

py-shiny/shiny/_docstring.py

Lines 158 to 161 in ec16ca9

	f"::warning file={file},line={func.__code__.co_firstlineno}::{fn_name} - {e}"
	)
	else:
	print(f"::warning file={file}::{fn_name} - {e}")

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Screenshot of annotations at the time