feat: add `previousSortColumns` to `onSort` and `onBeforeSort` (#633)
feat: add `previousSortColumns` to `onSort` and `onBeforeSort` (#633)

* chore: add missing event argument from last commit

* feat: add `previousSortColumns` to `onSort` and `onBeforeSort`
- in my use case, I want to cancel sort when backend server throws an error and to properly revert the sort, I need a reference to the previous sort
6pac/SlickGrid,6pac/SlickGrid