fix: detect node21.1.0

Author: Uzlopak

src/core/env.ts

@@ -37,7 +37,10 @@ else if (typeof document === 'undefined' && typeof self !== 'undefined') {
     // In worker
     env.worker = true;
 }
-else if (typeof navigator === 'undefined') {
+else if (
+    typeof navigator === 'undefined' ||
+    navigator.userAgent.indexOf('Node.js') === 0
+) {
     // In node
     env.node = true;
     env.svgSupported = true;