make file system internal

src/ImageSharp/IO/IFileSystem.cs

@@ -9,7 +9,7 @@ namespace SixLabors.ImageSharp.IO
     /// <summary>
     /// A simple interface representing the filesystem.
     /// </summary>
-    public interface IFileSystem
+    internal interface IFileSystem
     {
         /// <summary>
         /// Returns a readable stream as defined by the path.

src/ImageSharp/IO/LocalFileSystem.cs

@@ -12,7 +12,7 @@ namespace SixLabors.ImageSharp.IO
     /// <summary>
     /// A wrapper around the local File apis.
     /// </summary>
-    public class LocalFileSystem : IFileSystem
+    internal class LocalFileSystem : IFileSystem
     {
         /// <inheritdoc/>
         public Stream OpenRead(string path)