Export StreamType to expose Stream's type to users of the library, ra…

…ther than the entire class

native_client/javascript/index.ts

@@ -65,7 +65,7 @@ export interface Metadata {
  * Provides an interface to a DeepSpeech stream. The constructor cannot be called
  * directly, use :js:func:`Model.createStream`.
  */
-export class Stream {
+class Stream {
     /** @internal */
     _impl: any;
 
@@ -134,6 +134,12 @@ export class Stream {
         return result;
     }
 }
+/**
+ * Exposes the type of Stream without actually exposing the class.
+ * Because the Stream class should not be instantiated directly, 
+ * but instead be created via :js:func:`Model.createStream`.
+ */
+export type StreamType = Stream;
 
 /**
  * An object providing an interface to a trained DeepSpeech model.