Normative: Add Temporal.Now[@@toStringTag]

As per the July 2021 TC39 meeting, this should have the value
"Temporal.Now".

polyfill/lib/now.mjs

@@ -49,3 +49,9 @@ export const Now = {
   zonedDateTime,
   zonedDateTimeISO
 };
+Object.defineProperty(Now, Symbol.toStringTag, {
+  value: 'Temporal.Now',
+  writable: false,
+  enumerable: false,
+  configurable: true
+});

polyfill/test/Now/toStringTag/prop-desc.js

@@ -0,0 +1,15 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal-now-@@tostringtag
+includes: [propertyHelper.js]
+features: [Symbol.toStringTag, Temporal]
+---*/
+
+verifyProperty(Temporal.Now, Symbol.toStringTag, {
+  value: "Temporal.Now",
+  writable: false,
+  enumerable: false,
+  configurable: true,
+});

polyfill/test/Now/toStringTag/string.js

@@ -0,0 +1,9 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal-now-@@tostringtag
+features: [Symbol.toStringTag, Temporal]
+---*/
+
+assert.sameValue(String(Temporal.Now), "[object Temporal.Now]");

spec/temporal.html

@@ -79,6 +79,15 @@ <h1>The Temporal.Now Object</h1>
     <li>does not have a [[Call]] internal method; it cannot be invoked as a function.</li>
   </ul>
 
+  <emu-clause id="sec-value-properties-of-the-temporal-now-object">
+    <h1>Value Properties of the Temporal.Now Object</h1>
+    <emu-clause id="sec-temporal-now-@@tostringtag">
+      <h1>Temporal.Now [ @@toStringTag ]</h1>
+      <p>The initial value of the @@toStringTag property is the String value *"Temporal.Now"*.</p>
+      <p>This property has the attributes { [[Writable]]: *false*, [[Enumerable]]: *false*, [[Configurable]]: *true* }.</p>
+    </emu-clause>
+  </emu-clause>
+
   <emu-clause id="sec-function-properties-of-the-temporal-now-object">
     <h1>Function Properties of the Temporal.Now Object</h1>