KeyboardEvent.keyCode is deprecated (minor priority)

See [MDN](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/keyCode).

Usage [here](https://github.com/plotly/dash-table/blob/master/src/dash-table/components/ControlledTable/index.tsx#L134) and perhaps elsewhere.

Alternatives: `event.key` and `event.keyIdentifier`. Probably makes sense to keep `keyCode` as a fallback.