Merge pull request #2125 from Eitot/feature/destructive-action-highlighting

Enable hasDestructiveAction property of certain NSAlert buttons

On some alerts that are triggered by pressing the delete key,
highlight the "Delete" buttons in red instead of the accent colour
(on macOS 11+).

Author: barijaona

Vienna/Sources/Application/AppController.m

@@ -2038,6 +2038,9 @@ -(IBAction)deleteFolder:(id)sender
                                                                     NSBundle.mainBundle,
                                                                     @"Delete",
                                                                     @"Title of a button on an alert")];
+        if (@available(macOS 11, *)) {
+            alert.buttons.lastObject.hasDestructiveAction = YES;
+        }
         [alert addButtonWithTitle:NSLocalizedStringWithDefaultValue(@"cancel.button",
                                                                     nil,
                                                                     NSBundle.mainBundle,

Vienna/Sources/Main window/ArticleController.m

@@ -1167,6 +1167,9 @@ - (IBAction)delete:(nullable id)sender
                                                                     NSBundle.mainBundle,
                                                                     @"Delete",
                                                                     @"Title of a button on an alert")];
+        if (@available(macOS 11, *)) {
+            alert.buttons.lastObject.hasDestructiveAction = YES;
+        }
         [alert addButtonWithTitle:NSLocalizedStringWithDefaultValue(@"cancel.button",
                                                                     nil,
                                                                     NSBundle.mainBundle,