enhance: Save Preferences after switched Workspace and closed Preferences (#1073)

src/ViewModels/Launcher.cs

@@ -525,6 +525,7 @@ namespace SourceGit.ViewModels
             }
 
             _ignoreIndexChange = false;
+            Preferences.Instance.Save();
             GC.Collect();
         }
 

src/Views/Preferences.axaml.cs

@@ -189,6 +189,7 @@ namespace SourceGit.Views
                     new Commands.Config(null).Set($"gpg.{GPGFormat.Value}.program", GPGExecutableFile);
             }
 
+            ViewModels.Preferences.Instance.Save();
             base.OnClosing(e);
         }