fix produced .d.ts

- fix index.d.ts to properly use commonjs "export =" syntax
- output the native .d.ts. while the end user should not
  need to call C++ methods, this way we reduce transitive
  typechecking errors.

index.d.ts

@@ -1,10 +1,10 @@
 export * from "./build/types/AudioCodecs";
 
-export type { default as AudioDecoder } from "./build/types/AudioDecoder";
-export type { default as AudioEncoder } from "./build/types/AudioEncoder";
+export type AudioDecoder = import("./build/types/AudioDecoder");
+export type AudioEncoder = import("./build/types/AudioEncoder");
+export type AudioEncoderIncomingStreamTrack = import("./build/types/AudioEncoderIncomingStreamTrack");
 
 export type {
-	default as IncomingStreamTrackBridge,
 	ActiveEncodingInfo, ActiveLayersInfo,
 	EncodingStats, LayerStats, MediaStats, PacketWaitTime, TrackStats,
 } from "./build/types/AudioEncoderIncomingStreamTrack";

package.json

@@ -4,7 +4,7 @@
   "description": "Audio codecs for Media and RTMP servers",
   "main": "index.js",
   "scripts": {
-    "prepare": "tsc --checkJs false",
+    "prepare": "tsc --checkJs false && mkdir -p build/src && cp src/*.d.ts build/src",
     "check": "tsc --noEmit --emitDeclarationOnly false",
     "configure": "node-gyp configure",
     "swig": "swig -javascript -node -c++ src/audio-codecs.i",