Add the new method names to Array.prototype [ @@unscopables ] (#35)

* Add the new method names to Array.prototype [ @@unscopables ]

* Update spec.emu

Co-authored-by: Jordan Harband <ljharb@gmail.com>

Co-authored-by: Jordan Harband <ljharb@gmail.com>

Author: legendecas

spec.emu

@@ -115,4 +115,30 @@ location: https://tc39.es/proposal-array-grouping/
     </emu-alg>
   </emu-clause>
   </ins>
+
+  <emu-clause id="sec-array.prototype-@@unscopables">
+    <h1>Array.prototype [ @@unscopables ]</h1>
+    <p>The initial value of the @@unscopables data property is an object created by the following steps:</p>
+    <emu-alg>
+      1. Let _unscopableList_ be ! OrdinaryObjectCreate(*null*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"at"*, *true*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"copyWithin"*, *true*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"entries"*, *true*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"fill"*, *true*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"find"*, *true*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"findIndex"*, *true*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"flat"*, *true*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"flatMap"*, *true*).
+      1. <ins>Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"groupBy"*, *true*).</ins>
+      1. <ins>Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"groupByToMap"*, *true*).</ins>
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"includes"*, *true*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"keys"*, *true*).
+      1. Perform ! CreateDataPropertyOrThrow(_unscopableList_, *"values"*, *true*).
+      1. Return _unscopableList_.
+    </emu-alg>
+    <p>This property has the attributes { [[Writable]]: *false*, [[Enumerable]]: *false*, [[Configurable]]: *true* }.</p>
+    <emu-note>
+      <p>The own property names of this object are property names that were not included as standard properties of `Array.prototype` prior to the ECMAScript 2015 specification. These names are ignored for `with` statement binding purposes in order to preserve the behaviour of existing code that might use one of these names as a binding in an outer scope that is shadowed by a `with` statement whose binding object is an Array.</p>
+    </emu-note>
+  </emu-clause>
 </emu-clause>