build(deps-dev): bump tsdown from 0.20.3 to 0.21.0 (#295)

Bumps [tsdown](https://github.com/rolldown/tsdown) from 0.20.3 to 0.21.0.
- [Release notes](https://github.com/rolldown/tsdown/releases)
- [Commits](rolldown/tsdown@v0.20.3...v0.21.0)

---
updated-dependencies:
- dependency-name: tsdown
  dependency-version: 0.21.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

package.json

@@ -26,7 +26,7 @@
     "prop-types-table": "^2.0.0",
     "react": "^18.0.0",
     "react-dom": "^18.0.0",
-    "tsdown": "^0.20.3",
+    "tsdown": "^0.21.0",
     "typescript": "~5.9.0",
     "typescript-eslint": "^8.54.0",
     "vitest": "^4.0.18"