Add AggregateError

spec.html

@@ -32,9 +32,22 @@
   }
 </style>
 
-<emu-clause id="sec-native-error-types-used-in-this-standard-aggregatenerror">
-  <h1>AggregateError</h1>
-  <p>TODO implement</p>
+<emu-clause id="sec-native-error-types-used-in-this-standard-aggregateerror">
+  <h1>AggregateError ( errors, message )</h1>
+  <p>When the *AggregateError* function is called with arguments _errors_ and _message_, the following steps are taken:</p>
+  <emu-alg>
+    1. If NewTarget is *undefined*, let _newTarget_ be the active function object, else let _newTarget_ be NewTarget.
+    1. Let O be ? OrdinaryCreateFromConstructor(_newTarget_, `"%AggregateErrorPrototype%"`, « [[ErrorData]] »).
+    1. Let _errorsIterator_ be ? GetMethod(_errors_, @@iterator).
+    1. Let _errorsList_ ? IterableToList(_errors_, _errorsIterator_).
+    1. Let _errorsArray_ be CreateArrayFromList(_errorsList_).
+    1. Perform ! CreateDataProperty(_O_, `"errors"`, _errorsArray_).
+    1. If _message_ is not _undefined_, then
+      1. Let msg be ? ToString(_message_).
+      1. Let msgDesc be the PropertyDescriptor { [[Value]]: _msg_, [[Writable]]: *true*, [[Enumerable]]: *false*, [[Configurable]]: *true* }.
+      1. Perform ! DefinePropertyOrThrow(_O_, `"message"`, _msgDesc_).
+    1. Return _O_.
+  </emu-alg>
 </emu-clause>
 
 <emu-intro id="intro">