deps: support node 21 (#1018)

Author: GeoffreyBooth

package.json

@@ -84,6 +84,6 @@
     "check-coverage": false
   },
   "engines": {
-    "node": "18.x || 20.x"
+    "node": "18.x || 20.x || 21.x"
   }
 }