decal system & crayons (#5183)

Co-authored-by: Paul <ritter.paul1+git@googlemail.com>

Content.Shared/Decals/DecalChunkUpdateEvent.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Decals
+{
+    [Serializable, NetSerializable]
+    public class DecalChunkUpdateEvent : EntityEventArgs
+    {
+        public Dictionary<GridId, Dictionary<Vector2i, Dictionary<uint, Decal>>> Data = new();
+    }
+}