feat: Implemented FileSavePicker on MacOS

src/Uno.UWP/Storage/Pickers/FileSavePicker.cs

@@ -12,6 +12,6 @@ public partial class FileSavePicker
 
 		public string CommitButtonText { get; set; }
 
-		public IDictionary<string, IList<string>> FileTypeChoices { get; set; } = new Dictionary<string, IList<string>>();
+		public IDictionary<string, IList<string>> FileTypeChoices { get; } = new Dictionary<string, IList<string>>();
 	}
 }

src/Uno.UWP/Storage/Pickers/FileSavePicker.macOS.cs

@@ -18,7 +18,7 @@ private async Task<StorageFile> PickFileTaskAsync()
 			var savePicker = new NSSavePanel();
 			savePicker.DirectoryUrl = new NSUrl(GetStartPath(), true);
 			savePicker.AllowedFileTypes = GetFileTypes();
-			if(SuggestedFileName != null)
+			if (SuggestedFileName != null)
 			{
 				savePicker.NameFieldStringValue = SuggestedFileName;
 			}
@@ -43,12 +43,11 @@ private string GetStartPath()
 				PickerLocationId.PicturesLibrary => Environment.SpecialFolder.MyPictures,
 				PickerLocationId.VideosLibrary => Environment.SpecialFolder.MyVideos,
 				_ => Environment.SpecialFolder.Personal
-
 			};
 
 			return Environment.GetFolderPath(specialFolder);
 		}
 
-		private string[] GetFileTypes() => FileTypeChoices.SelectMany(x => x.Value.Select(val=>val.TrimStart(new[] { '.' }))).ToArray();
+		private string[] GetFileTypes() => FileTypeChoices.SelectMany(x => x.Value.Select(val => val.TrimStart(new[] { '.' }))).ToArray();
 	}
 }

src/Uno.UWP/Storage/Pickers/PickerLocationId.cs

@@ -1,39 +1,16 @@
 namespace Windows.Storage.Pickers
 {
-
-
 	public enum PickerLocationId
 	{
-
 		DocumentsLibrary,
-
-
 		ComputerFolder,
-
-
 		Desktop,
-
-
 		Downloads,
-
-
 		HomeGroup,
-
-
 		MusicLibrary,
-
-
 		PicturesLibrary,
-
-
 		VideosLibrary,
-
-
 		Objects3D,
-
-
-		Unspecified,
-
+		Unspecified
 	}
-
-}
+}