flattenObject doesn't handle array of objects

[mkatrenik]

Given this code

    const result = flattenObject({
      a: [1, { b: 2 }, 3],
    });

    expect(result).toEqual({
      'a.0': 1,
      'a.1.b': 2,
      'a.2': 3,
    });

nested object is not flattened