Update README.md (#721)

Updates documentation for `shouldCancelStart` to indicate `button` types are also cancelled by default.

Author: rubencodes

README.md

@@ -106,7 +106,7 @@ There are already a number of great Drag & Drop libraries out there (for instanc
 | pressDelay                        | Number                                                    | `0`                                                                                                            | If you'd like elements to only become sortable after being pressed for a certain time, change this property. A good sensible default value for mobile is `200`. Cannot be used in conjunction with the `distance` prop.                                                                                                                                                                                                                                                |
 | pressThreshold                    | Number                                                    | `5`                                                                                                            | Number of pixels of movement to tolerate before ignoring a press event.                                                                                                                                                                                                                                                                                                                                                                                                |
 | distance                          | Number                                                    | `0`                                                                                                            | If you'd like elements to only become sortable after being dragged a certain number of pixels. Cannot be used in conjunction with the `pressDelay` prop.                                                                                                                                                                                                                                                                                                               |
-| shouldCancelStart                 | Function                                                  | [Function](https://github.com/clauderic/react-sortable-hoc/blob/master/src/SortableContainer/index.js#L48)     | This function is invoked before sorting begins, and can be used to programatically cancel sorting before it begins. By default, it will cancel sorting if the event target is either an `input`, `textarea`, `select` or `option`.                                                                                                                                                                                                                                     |
+| shouldCancelStart                 | Function                                                  | [Function](https://github.com/clauderic/react-sortable-hoc/blob/master/src/SortableContainer/index.js#L48)     | This function is invoked before sorting begins, and can be used to programatically cancel sorting before it begins. By default, it will cancel sorting if the event target is either an `input`, `textarea`, `select`, `option`, or `button`.                                                                                                                                                                                                                                     |
 | updateBeforeSortStart             | Function                                                  |                                                                                                                | This function is invoked before sorting begins. It can return a promise, allowing you to run asynchronous updates (such as `setState`) before sorting begins. `function({node, index, collection, isKeySorting}, event)`                                                                                                                                                                                                                                               |
 | onSortStart                       | Function                                                  |                                                                                                                | Callback that is invoked when sorting begins. `function({node, index, collection, isKeySorting}, event)`                                                                                                                                                                                                                                                                                                                                                               |
 | onSortMove                        | Function                                                  |                                                                                                                | Callback that is invoked during sorting as the cursor moves. `function(event)`                                                                                                                                                                                                                                                                                                                                                                                         |