Custom Class JSON Serialization

I have a gamestate class that I made completely serializable. However, I want to convert ONLY an instance of this class to json and save it to local storage. I've looked through a couple packages and they all seem to do to much.

so, all I want is just to save this simple class to json. And preferably with no 3rd party packages.

 [System.Serializable]
 public class GameState {
     public float taxRate = 1;
     public float might = 0;
     public float unrest = 0;
     public int money = 180;
     public int day = 1;
     public float difficulty = 0.5f;
     public float spawnRate = 0.1f;
     public string currentScene;
     public bool inaugurated = false;
     public float birthRate = 0.1f;
     public float interestRate = 0.5f;
     [SerializeField]
     public List<Citizen>[,] people = new List<Citizen>[3,3];
     [SerializeField]
     public List<Badge> force = new List<Badge>();
     [SerializeField]
     public List<Occurance> occurances = new List<Occurance>();
     [SerializeField]
     public List<Story> news = new List<Story>();
 }