add basic dialogue system and interactable interface

Assets/Interactable.cs

@@ -0,0 +1,11 @@
+using UnityEngine;
+
+public abstract class Interactable : MonoBehaviour
+{
+    public abstract void Interact();
+
+    // for entering/exiting trigger regions
+    public abstract void MoveInsideRange();
+
+    public abstract void MoveOutsideRange();
+}