Tauri-demo: add onAuthStateChange callback call to login and signup emulators

auth.spec.ts

function setLogin(firebaseAuth: any, successful: boolean) {
    (firebaseAuth.signInWithEmailAndPassword as any).mockImplementation(async () => {
        const user = {
            uid: '123',
            email: '[email protected]'
        };

        (firebaseAuth.getAuth as any).mockReturnValue({
            currentUser: successful ? user : null
        });

        if (successful) firebaseAuth.authChangeCallback();

        return {
            user
        };
    });
}

function setSignUp(firebaseAuth: any, successful: boolean) {
    (firebaseAuth.createUserWithEmailAndPassword as any).mockImplementation(async () => {
        const user = {
            uid: '123',
            email: '[email protected]'
        };

        (firebaseAuth.getAuth as any).mockReturnValue({
            currentUser: successful ? user : null
        });

        if (successful) firebaseAuth.authChangeCallback();

        return {
            user
        };
    });
}