Add article, code projects, toc, and redirects (#1178)

Co-authored-by: Andy (Steve) De George <[email protected]>

dotnet-desktop-guide/net/wpf/toc.yml

@@ -88,6 +88,10 @@ items:
       href: properties/how-to-register-an-attached-property.md
     - name: Collection-type dependency properties
       href: properties/collection-type-dependency-properties.md
+    - name: Common tasks
+      items:
+      - name: Attached properties
+        href: properties/attached-properties-overview.md
   - name: Resources
     items:
     - name: Overview