fix(ember__error): make EmberError extendable (#29337)

types/ember/index.d.ts

@@ -228,7 +228,7 @@ export namespace Ember {
     /**
      * A subclass of the JavaScript Error object for use in Ember.
      */
-    const Error: EmberError;
+    const Error: typeof EmberError;
 
     const Evented: typeof EmberObjectEventedNs.default;
 

types/ember__error/ember__error-tests.ts

@@ -1,3 +1,7 @@
 import Error from '@ember/error';
 
-new Error('Fuuuuuuuu'); // $ExpectType Error
+new Error('Fuuuuuuuu'); // $ExpectType EmberError
+
+// allows to extend from EmberError
+class AjaxError extends Error {
+}

types/ember__error/index.d.ts

@@ -7,4 +7,4 @@
 /**
  * A subclass of the JavaScript Error object for use in Ember.
  */
-export default ErrorConstructor;
+export default class EmberError extends Error {}