docs: add wrappers to wrapper-array/README.md (#280)

Author: 38elements

docs/en/api/wrapper-array/README.md

@@ -4,6 +4,7 @@ A `WrapperArray` is an object that contains an array of [`Wrappers`](../wrapper/
 
 - **Properties:**
 
+`wrappers` `array`: the `Wrappers` contained in the `WrapperArray`  
 `length` `number`: the number of `Wrappers` contained in the `WrapperArray`
 
  - **Methods:**