chore(deps): update dependency tsdown to ^0.20.0

Author: renovate[bot]

@iconify/tools/package.json

@@ -44,7 +44,7 @@
 		"globals": "^16.5.0",
 		"prettier": "^3.7.4",
 		"rimraf": "^6.1.2",
-		"tsdown": "^0.18.3",
+		"tsdown": "^0.20.0",
 		"typescript": "^5.9.3",
 		"vitest": "^4.0.16"
 	},