Improve the error message for dynamic css functions when returning invalid values

[jantimon]

When a styled component's dynamic prop function returns an invalid value (like undefined from a missing prop), the error message now includes the actual function that caused the issue.

Before:

Error: Dynamic CSS functions must return a string or number but returned undefined

After:

Error: Dynamic CSS functions must return a string or number but returned undefined

Dynamic CSS function: (p) => p.$groupColor

Fixes #229

[changeset-bot]

🦋 Changeset detected

Latest commit: 6a6a0a3

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
next-yak	Patch

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[codspeed-hq]

CodSpeed Performance Report

Merging #230 will not alter performance

_{Comparing dynamic-functions-error-message (6a6a0a3) with main (4068803)}

Summary

✅ 2 untouched benchmarks

[Mad-Kat]

A test case with the actual error message would be nice for the next time we encounter this. Wdyt?