refactor<*>: rewrite all with AvaloniaUI

src/ViewModels/DeleteRepositoryNode.cs

@@ -0,0 +1,22 @@
+using System.Threading.Tasks;
+
+namespace SourceGit.ViewModels {
+    public class DeleteRepositoryNode : Popup {
+        public RepositoryNode Node {
+            get => _node;
+            set => SetProperty(ref _node, value);
+        }
+
+        public DeleteRepositoryNode(RepositoryNode node) {
+            _node = node;
+            View = new Views.DeleteRepositoryNode() { DataContext = this };
+        }
+
+        public override Task<bool> Sure() {
+            Preference.RemoveNode(_node);
+            return null;
+        }
+
+        private RepositoryNode _node = null;
+    }
+}