add basic dialogue system and interactable interface

Assets/GameManager.cs

@@ -0,0 +1,24 @@
+using UnityEngine;
+
+public class GameManager : MonoBehaviour
+{
+    public static GameManager Instance { get; private set; }
+    public DialogueManager DialogueManager { get; private set; }
+
+    private void Awake()
+    {
+        // If there is an instance, and it's not me, delete myself.
+
+        if (Instance != null && Instance != this)
+        {
+            Destroy(this);
+        }
+        else
+        {
+            Instance = this;
+            DontDestroyOnLoad(gameObject);
+
+            DialogueManager = GetComponent<DialogueManager>();
+        }
+    }
+}