Make VectorTileEncoder.Encode return the stream for fluent API usage

Co-authored-by: bertt <538812+bertt@users.noreply.github.com>

Author: Copilot

README.md

@@ -48,11 +48,10 @@ layer.VectorTileFeatures.Add(feature);
 
 // Encode to stream
 var layers = new List<VectorTileLayer> { layer };
-var outputStream = new MemoryStream();
-VectorTileEncoder.Encode(layers, outputStream);
+var stream = VectorTileEncoder.Encode(layers, new MemoryStream());
 
 // Save to file
-File.WriteAllBytes("output.pbf", outputStream.ToArray());
+File.WriteAllBytes("output.pbf", ((MemoryStream)stream).ToArray());
 ```
 
 Tip: If you use this library with vector tiles loading from a webserver, you could run into the following exception: 

src/VectorTileEncoder.cs

@@ -6,7 +6,7 @@ namespace Mapbox.Vector.Tile;
 
 public static class VectorTileEncoder
 {
-    public static void Encode(List<VectorTileLayer> layers, Stream stream)
+    public static Stream Encode(List<VectorTileLayer> layers, Stream stream)
     {
         var tile = new Tile();
 
@@ -48,5 +48,6 @@ public static void Encode(List<VectorTileLayer> layers, Stream stream)
         }
 
         Serializer.Serialize(stream, tile);
+        return stream;
     }
 }