[react-dom] Change charCode to number
[react-dom] Change charCode to number

Changed SyntheticEventData.charCode to number in order to match
the properties listed here:

https://reactjs.org/docs/events.html#keyboard-events

markogresak/DefinitelyTyped,mcliment/DefinitelyTyped,dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,georgemarshall/DefinitelyTyped,georgemarshall/DefinitelyTyped,borisyankov/DefinitelyTyped,borisyankov/DefinitelyTyped,georgemarshall/DefinitelyTyped,dsebastien/DefinitelyTyped