fix(docs): Move NativeScriptError declaration to a separate file (#6927)

It is used by `application.d.ts` and needs to be documented. The reason
that it wasn't included in the documentation by now is that `tns-core-modules.d.ts`
(which imports `module.d.ts`) defines types which are part of the internal
modules and runtimes APIs. As such they are excluded from the generation
of API documentation.

tns-core-modules/application/application-common.ts

@@ -39,7 +39,7 @@ import {
     iOSApplication,
     LoadAppCSSEventData,
     UnhandledErrorEventData,
-    DiscardedErrorEventData
+    DiscardedErrorEventData,
 } from "./application";
 
 export { UnhandledErrorEventData, DiscardedErrorEventData, CssChangedEventData, LoadAppCSSEventData };

tns-core-modules/application/application.d.ts

@@ -2,8 +2,8 @@
  * Contains the application abstraction with all related methods.
  * @module "application"
  */ /** */
+/// <reference path="../nativescript-error.d.ts" />
 
-///<reference path="../tns-core-modules.d.ts" /> Include global typings
 import { NavigationEntry, View, Observable, EventData } from "../ui/frame";
 
 /**
@@ -607,4 +607,4 @@ export function hasLaunched(): boolean;
 
 export interface LoadAppCSSEventData extends EventData {
     cssFile: string;
-}
+}