Update TypeScript definitions

[DarkMatterMatt]

Hi there 👋

Breaking changes:

• Fix App.listen() callback parameter type definitions. This is a breaking change if anyone was incorrectly using the types before.

Non-breaking changes:

• Update comment for maxBackpressure - default is now 64KB (updated in https://github.com/uNetworking/uWebSockets/commit/20fbdbb7aed6f303caef38eadc1a7ee3aac2e95e)
• Add closeOnBackpressureLimit (added in https://github.com/uNetworking/uWebSockets.js/commit/5d6a9c51941ff472a7665549a5de493f8a2618d7)
• Type us_listen_socket extends us_socket (as per uSocket's internal.h)

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Two related notes

1. At the moment closeOnBackpressureLimit and sendPingsAutomatically are Int32Value in AppWrapper.h, should these be BooleanValue?
2. At the moment the native types have compatible interfaces which means that us_socket_context_t or any object can be used in places that only accept a us_listen_socket. I think that you could do something like this to avoid that happening:

   export interface us_listen_socket extends us_socket {
   _us_listen_socket: never;
   }
   export interface us_socket {
   _us_socket: never;
   }
   export interface us_socket_context_t {
   _us_socket_context_t: never;
   }

   This isn't perfect (as users could attempt to use listenToken._us_listen_socket), but imo it's an improvement. Do you think this something worth raising an issue for?