Added missing using

Author: hishitetsu

src/Files.App/Helpers/BitmapHelper.cs

@@ -1,7 +1,9 @@
 using Files.App.Filesystem;
 using Files.App.Filesystem.StorageItems;
 using Microsoft.UI.Xaml.Media.Imaging;
+using System;
 using System.IO;
+using System.Threading.Tasks;
 using Windows.Graphics.Imaging;
 using Windows.Storage;
 using Windows.Storage.Streams;

src/Files.App/Helpers/FileOperationsHelpers.cs

@@ -2,12 +2,22 @@
 using Files.App.Filesystem.Security;
 using Files.App.Shell;
 using Files.Backend.Helpers;
+using Files.Shared;
+using Files.Shared.Enums;
+using Files.Shared.Extensions;
 using Microsoft.Extensions.Logging;
 using Microsoft.Win32;
+using System;
 using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics;
 using System.IO;
+using System.Linq;
 using System.Runtime.InteropServices;
 using System.Security.Principal;
+using System.Threading;
+using System.Threading.Tasks;
 using Tulpep.ActiveDirectoryObjectPicker;
 using Vanara.PInvoke;
 using Vanara.Windows.Shell;