Update useRowSelect.md (#1948)
Update useRowSelect.md (#1948)

Missing documentation for `getToggleRowSelectedProps`, used on the [example](https://codesandbox.io/s/github/tannerlinsley/react-table/tree/master/examples/row-selection).

The `indeterminate` field is not documented at all, and I wonder what's the difference to the `checked` field.
react-tools/react-table,tannerlinsley/react-table