fix: allow no instanceConfig and use {}

Author: ModyQyW

packages/core/src/core/Un.test.ts

@@ -0,0 +1,10 @@
+import { describe, expect, it } from "vitest";
+import { Un } from "./Un";
+
+describe("Axios", () => {
+  it("should not throw if the config argument is omitted", () => {
+    const un = new Un();
+
+    expect(un.defaults).toStrictEqual({});
+  });
+});

packages/core/src/core/Un.ts

@@ -15,7 +15,7 @@ export class Un<T = UnData, D = UnData> {
     response: UnInterceptorManager<UnResponse<T, D>, T, D>;
   };
 
-  constructor(instanceConfig: UnConfig<T, D>) {
+  constructor(instanceConfig?: UnConfig<T, D>) {
     this.defaults = instanceConfig || {};
     this.interceptors = {
       request: new UnInterceptorManager(),