Change the keys for Game.map.describeExits to be actual directions

[tiennou]

Brief Description

This makes it at least a bit clearer why the keys are odd numbers.

Checklists

• Test passed
• Coding style (indentation, etc)
• Edits have been made to src/ files not index.d.ts
• Run npm run dtslint to update index.d.ts

[DiamondMofeng]

This changes the type of ExitKey from string to number, So I was a little hesitant...
Maybe we need to investigate how player use this in their code

[tiennou]

I think the issue I had is that the forced stringification of keys makes something like the following break:

const exits = Game.map.describeExits("room");
for (const dir in exits) {
  if (dir === EXIT_TOP) { /* … */ } // "Never true" TS error
}

But either way, that code doesn't even fix that issue, so I guess it could be dropped.

[tiennou]

Closing, since it's not as useful as I thought, and could actually be dangerous if you end up trusting the number type you could get back with a strict comparison.