Add tests for useSignInAnonymouslyMutation hook

[HassanBahati]

this pr adds tests to useSignInAnonymouslyMutation hook

[docs-page]

To view this pull requests documentation preview, visit the following URL:

react-query-firebase.invertase.dev/~103

Documentation is deployed and generated using docs.page.

[HassanBahati]

@Ehesp i did have 2 options here when mocking the firebase auth module

1. Option One (seemed simple and its what i went with)

// this ignores all other imports from the module 
// and only mocks the specific function 'signInAnonymously'
vi.mock("firebase/auth", () => ({
  signInAnonymously: vi.fn(),
}));

3. Option Two

//
vi.mock("firebase/auth", async (importOriginal) => {
  // Import the original 'firebase/auth' module
  const module = await importOriginal<typeof import("firebase/auth")>();

  // Return a mocked version of the module
  return {
    ...module, // Spread in all the original functions from the module
    signInAnonymously: vi.fn(), // Mock the specific function 'signInAnonymously'
  };
});

do you think it would be better to with option 2 that returns a mocked version of the module with all original functions ?