update default for contextual help

Author: snowystinger

packages/@react-spectrum/s2/src/ContextualHelp.tsx

@@ -37,6 +37,11 @@ export interface ContextualHelpProps extends
   placement?: Placement,
   /** Contents of the Contextual Help popover. */
   children: ReactNode,
+  /**
+   * The offset of the popover from the trigger button.
+   * @default 8
+   */
+  offset?: number,
   /**
    * The size of the ActionButton.
    *