[@pmndrs/pointer-events] TypeScript build error introduced in #472

[nyan-left]

PR #472 added a pointerover event listener but didn't add 'over' to the InternalEventType union, causing tsc to fail:

src/forward.ts:159:12 - error TS2678: Type '"over"' is not comparable to type 'InternalEventType'.

159       case 'over':
               ~~~~~~
src/forward.ts:204:50 - error TS2345: Argument of type '"over"' is not assignable to parameter of type 'InternalEventType'.
204   const pointerOverListener = onEvent.bind(null, 'over')
                                                     ~~~~~~
Found 2 errors in the same file, starting at: src/forward.ts:159