showDirectoryPicker always returns 1 handle (#443)

Author: vapier

index.bs

@@ -845,7 +845,7 @@ these steps:
   :: Shows a directory picker that lets the user select a single directory, returning a handle for
     the selected directory if the user grants read permission.
 
-  : handles = await window . {{Window/showDirectoryPicker()}}({ {{DirectoryPickerOptions/mode}}: 'readwrite' })
+  : |handle| = await window . {{Window/showDirectoryPicker()}}({ {{DirectoryPickerOptions/mode}}: 'readwrite' })
   :: Shows a directory picker that lets the user select a single directory, returning a handle for
     the selected directory. The user agent can combine read and write permission requests on this handle into
     one subsequent prompt.