add reducer

src/Updux.ts

@@ -50,4 +50,8 @@ export class Updux<TState extends any = {}, TActions extends { [key: string]: Ac
             R.mapValues(this.#subduxes, ({ initial }) => initial),
         );
     }
+
+    get reducer() {
+        return (state, action) => state;
+    }
 }

src/reducer.test.ts

@@ -0,0 +1,11 @@
+import { test, expect } from 'vitest';
+
+import { Updux } from './Updux.js';
+
+test('basic reducer', () => {
+    const dux = new Updux({});
+
+    expect(dux.reducer).toBeTypeOf('function');
+
+    expect(dux.reducer({ a: 1 }, { type: 'foo' })).toMatchObject({ a: 1 }); // noop
+});