docs: add missing props to UI components (#13247)

www/apps/ui/specs/components/DropdownMenu/DropdownMenu.Content.json

@@ -8,7 +8,7 @@
         "value": "8",
         "computed": false
       },
-      "description": "",
+      "description": "The space in pixels between the dropdown menu and its trigger element.",
       "required": false
     },
     "collisionPadding": {
@@ -16,7 +16,7 @@
         "value": "8",
         "computed": false
       },
-      "description": "",
+      "description": "The distance in pixels from the boundary edges where collision detection should occur.",
       "required": false
     },
     "align": {
@@ -24,7 +24,7 @@
         "value": "\"center\"",
         "computed": false
       },
-      "description": "",
+      "description": "The alignment of the dropdown menu relative to its trigger element.\n\n@defaultValue center",
       "required": false
     }
   }