README: escape pipe char

Author: computerjazz

README.md

@@ -38,7 +38,7 @@ All props are spread onto underlying [FlatList](https://facebook.github.io/react
 | :------------------------- | :---------------------------------------------------------------------------------------- | :-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 | `data`                     | `T[]`                                                                                     | Items to be rendered.                                                                                                                                                                                              |
 | `ref`                     | `React.RefObject<FlatList<T>>`                                                                                     | FlatList ref to be forwarded to the underlying FlatList.                                                                                                                                                                                      |
-| `renderItem`               | `(params: { item: T, getIndex: () => number | undefined, drag: () => void, isActive: boolean}) => JSX.Element` | Call `drag` when the row should become active (i.e. in an `onLongPress` or `onPressIn`).                                                                                                                           |
+| `renderItem`               | `(params: { item: T, getIndex: () => number \| undefined, drag: () => void, isActive: boolean}) => JSX.Element` | Call `drag` when the row should become active (i.e. in an `onLongPress` or `onPressIn`).                                                                                                                           |
 | `renderPlaceholder`        | `(params: { item: T, index: number }) => React.ReactNode`                                 | Component to be rendered underneath the hovering component                                                                                                                                                         |
 | `keyExtractor`             | `(item: T, index: number) => string`                                                      | Unique key for each item                                                                                                                                                                                           |
 | `onDragBegin`              | `(index: number) => void`                                                                 | Called when row becomes active.                                                                                                                                                                                    |