feat: add WorldConstants, SurfacePalette and IBiome contract

World/WorldGen/WorldConstants.cs

@@ -0,0 +1,10 @@
+using VoxelChunk = VoxelEngine.World.Chunk.Chunk;
+
+namespace VoxelEngine.World.WorldGen;
+
+public static class WorldConstants
+{
+    public const int WorldHeightChunks = 8;
+    public const int WorldHeight = WorldConstants.WorldHeightChunks * VoxelChunk.Size; // 128
+    public const int SeaLevel = 64;
+}