Added SelectFilesHandler

Toolkit.Foundation/SelectFilesHandler.cs

@@ -0,0 +1,20 @@
+namespace Toolkit.Foundation;
+
+public class SelectFilesHandler(IFileProvider fileProvider) :
+    IHandler<SelectionEventArgs<FileFilter>, IReadOnlyCollection<string>?>
+{
+    public async Task<IReadOnlyCollection<string>?> Handle(SelectionEventArgs<FileFilter> args,
+        CancellationToken cancellationToken)
+    {
+        if (args.Sender is FileFilter filter)
+        {
+            if (await fileProvider.SelectFiles(filter)
+                is { Count: > 0 } files)
+            {
+                return files;
+            }
+        }
+
+        return default;
+    }
+}

Toolkit.Foundation/SelectFoldersHandler.cs

@@ -1,5 +1,6 @@
 namespace Toolkit.Foundation;
 
+
 public class SelectFoldersHandler(IFolderProvider folderProvider) :
     IHandler<SelectionEventArgs<FolderFilter>, IReadOnlyCollection<string>?>
 {