add function for internal use

Svelto.ECS/DataStructures/TypeSafeDictionary.cs

@@ -34,6 +34,7 @@ namespace Svelto.ECS.Internal
         void Trim();
         void Clear();
         bool Has(int entityIdEntityId);
+        int GetFirstID();
     }
 
     class TypeSafeDictionary<TValue> : FasterDictionary<int, TValue>, ITypeSafeDictionary where TValue : IEntityStruct
@@ -80,6 +81,11 @@ namespace Svelto.ECS.Internal
             return ContainsKey(entityIdEntityId);
         }
 
+        public int GetFirstID()
+        {
+            return FasterValues[0].ID.entityID;
+        }
+
         void AddEntityViewToEngines(Dictionary<Type, FasterList<IHandleEntityViewEngineAbstracted>> entityViewEnginesDB, ref TValue entity)
         {
             FasterList<IHandleEntityViewEngineAbstracted> entityViewsEngines;