chore: readme updated

Author: betula

README.md

@@ -1,5 +1,27 @@
 ### Realar Jest example
 
+Example of easy unit testing with [Realar](https://github.com/betula/realar).
+
+```javascript
+import { mock } from "realar";
+import { Notifier, Api, UserForm } from "./user-form";
+
+test("User form should work", async () => {
+  const notifierMock = mock(Notifier, {
+    fail: jest.fn()
+  });
+  const apiMock = mock(Api, {
+    userSave: jest.fn().mockResolvedValue(0)
+  });
+
+  const form = new UserForm("a", "b");
+
+  await form.save();
+  expect(notifierMock.fail).toHaveBeenCalled();
+  expect(apiMock.userSave).toHaveBeenCalledWith("a", "b");
+});
+```
+
 Installation
 
 ```bash