Added game state and network client

Assets/Scripts/Network/ConnectionManager.cs

@@ -0,0 +1,48 @@
+using PashaBibko.PenguinChase.Extensions;
+using Unity.Netcode;
+using UnityEngine;
+
+namespace PashaBibko.PenguinChase.Network
+{
+    public class ConnectionManager : MonoBehaviour
+    {
+        private static ConnectionManager sInstance;
+
+        [SerializeField] private GameObject PrefabForEachClient;
+        public static GameObject ClientPrefab => sInstance?.PrefabForEachClient;
+
+        private void Awake()
+        {
+            // Stops overlapping instances
+            if (sInstance is not null)
+            {
+                Debug.LogError($"Multiple of [{nameof(ConnectionManager)}] cannot exist.");
+                Destroy(gameObject);
+                return;
+            }
+
+            sInstance = this;
+        }
+
+        public static void CreateNetworkConnectionManager()
+        {
+            NetworkManager.Singleton.OnClientConnectedCallback += OnClientJoin;
+            OnClientJoin(0); // Has to be manually called for local client
+        }
+
+        public static void DestroyNetworkConnectionManager()
+        {
+            NetworkManager.Singleton.OnClientConnectedCallback -= OnClientJoin;
+            sInstance.DestroyAllChildren();
+        }
+
+        private static void OnClientJoin(ulong id)
+        {
+            GameObject client = Instantiate(ClientPrefab);
+            DontDestroyOnLoad(client);
+            
+            NetworkObject networkObject = client.GetComponent<NetworkObject>();
+            networkObject.SpawnAsPlayerObject(id);
+        }
+    }
+}