feat(client): add handle429Backoff method for intelligent rate limit handling

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@push.rocks/smartrequest",
-  "version": "4.1.0",
+  "version": "4.2.0",
   "private": false,
   "description": "A module for modern HTTP/HTTPS requests with support for form data, file uploads, JSON, binary data, streams, and more.",
   "exports": {
@@ -10,7 +10,7 @@
   },
   "type": "module",
   "scripts": {
-    "test": "(tstest test/ --verbose)",
+    "test": "(tstest test/ --verbose --timeout 60)",
     "build": "(tsbuild --web)",
     "buildDocs": "tsdoc"
   },