doc: updated readme

Author: awais-ansari

src/plugin-slots/DesktopSecondaryMenuSlot/README.md

@@ -2,7 +2,7 @@
 
 | Slot ID | Description | Docs |
 |---------|-------------|------|
-| `org.openedx.frontend.layout.header_desktop_secondary_menu.v2` | Full secondary menu area: notification tray + menu items | [v2 docs](./v2/) |
+| `org.openedx.frontend.layout.header_desktop_secondary_menu.v2` | Full secondary menu area: notification tray + menu items (Default slot)| [v2 docs](./v2/) |
 | `org.openedx.frontend.layout.header_desktop_secondary_menu.v1` | Menu items only | [v1 docs](./v1/) |
 
 ### Slot ID Aliases