docs: Update README.rst

The coding example here had copied the names of a couple of components from a different example and so I think they're wrong and should be corrected to match the components imported in this example to reduce confusion.

Author: feanil

README.rst

@@ -125,12 +125,12 @@ file as well to define its plugin slots.
             {
               op: PLUGIN_OPERATIONS.Wrap,
               widgetId: 'default_contents',
-              wrapper: wrapWidget,
+              wrapper: wrapSidebar,
             },
             {
               op: PLUGIN_OPERATIONS.Modify,
               widgetId: 'social_media_link',
-              fn: modifyWidget,
+              fn: modifySidebar,
             },
           ]
         }