udate textarea to use destructuring, fix styling

snippets/TextArea.md

@@ -14,7 +14,7 @@ function TextArea ({ callback, cols = 20, rows = 2, disabled = false, readOnly =
       disabled={disabled}
       readOnly={readOnly}
       placeholder={placeholder}
-      onChange={(event) => callback(event.target.value)} 
+      onChange={({ target : { value } }) => callback(value)}
     />
   );
 }