docs: modify the format of Type (#55)

Author: cijiugechu

README.md

@@ -66,7 +66,7 @@ render(
 | bottom           | ReactNode                         |                | extra bottom area beneath footer columns |
 | theme            | 'light' \| 'dark'                 | 'dark'         | preset theme of footer                   |
 | backgroundColor  | string                            | '#000'         | background color of footer               |
-| columnLayout     | 'space-around' or 'space-between' | 'space-around' | justify-content value of columns element |
+| columnLayout     | 'space-around' \| 'space-between' | 'space-around' | justify-content value of columns element |
 | maxColumnsPerRow | number                            | -              | max count of columns for each row        |
 
 ### Column