JSRL, now with TypeScript support

I backported TypeScript support from Emerald Woods into JSRL, so you can now use it to create roguelikes with TypeScript out of the box.

Unlike Emerald Woods, which has had a gradual transition to TypeScript (because it’s so big), for JSRL I decided to migrate it completely in a single machete blow, with an additional pass to use proper typed classes instead of functions.

The reason why there are still many variables typed as any is that some modules were modeled as raw objects instead of classes, and typifying them will require some additional work.