add filesystem for webroot

zero.Core/FileStorage/WebRootFileSystem.cs

@@ -0,0 +1,28 @@
+namespace zero.Media;
+
+public class WebRootFileSystem : PhysicalFileSystem, IWebRootFileSystem
+{
+  protected string PublicPathPrefix { get; }
+
+
+  public WebRootFileSystem(string root, string publicPathPrefix) : base(root)
+  {
+    PublicPathPrefix = (publicPathPrefix ?? String.Empty).EnsureEndsWith('/');
+  }
+
+
+  /// <inheritdoc />
+  public override string MapToPublicPath(string path)
+  {
+    if (path.IsNullOrEmpty())
+    {
+      return null;
+    }
+    return PublicPathPrefix + path.TrimStart('/');
+  }
+}
+
+
+public interface IWebRootFileSystem : IFileSystem
+{
+}