Editorial: Add notes about extension points for ECMA-402

As per TC39 plenary, the specification should include informative notes
indicating where ECMA-402 extends prototypes with additional properties.

Closes: tc39#2169

Author: ptomato

spec/calendar.html

@@ -946,6 +946,10 @@ <h1>Properties of the Temporal.Calendar Prototype Object</h1>
       <li>has a [[Prototype]] internal slot whose value is %Object.prototype%.</li>
     </ul>
 
+    <emu-note>
+      An ECMAScript implementation that includes the ECMA-402 Internationalization API extends this prototype with additional properties in order to represent calendar data.
+    </emu-note>
+
     <emu-clause id="sec-temporal.calendar.prototype.constructor">
       <h1>Temporal.Calendar.prototype.constructor</h1>
       <p>The initial value of `Temporal.Calendar.prototype.constructor` is %Temporal.Calendar%.</p>

spec/plaindate.html

@@ -92,6 +92,10 @@ <h1>Properties of the Temporal.PlainDate Prototype Object</h1>
       <li>has a [[Prototype]] internal slot whose value is %Object.prototype%.</li>
     </ul>
 
+    <emu-note>
+      An ECMAScript implementation that includes the ECMA-402 Internationalization API extends this prototype with additional properties in order to represent calendar data.
+    </emu-note>
+
     <emu-clause id="sec-temporal.plaindate.prototype.constructor">
       <h1>Temporal.PlainDate.prototype.constructor</h1>
       <p>The initial value of `Temporal.PlainDate.prototype.constructor` is %Temporal.PlainDate%.</p>

spec/plaindatetime.html

@@ -95,6 +95,10 @@ <h1>Properties of the Temporal.PlainDateTime Prototype Object</h1>
       <li>has a [[Prototype]] internal slot whose value is %Object.prototype%.</li>
     </ul>
 
+    <emu-note>
+      An ECMAScript implementation that includes the ECMA-402 Internationalization API extends this prototype with additional properties in order to represent calendar data.
+    </emu-note>
+
     <emu-clause id="sec-temporal.plaindatetime.prototype.constructor">
       <h1>Temporal.PlainDateTime.prototype.constructor</h1>
       <p>The initial value of `Temporal.PlainDateTime.prototype.constructor` is %Temporal.PlainDateTime%.</p>

spec/plainmonthday.html

@@ -79,6 +79,10 @@ <h1>Properties of the Temporal.PlainMonthDay Prototype Object</h1>
       <li>has a [[Prototype]] internal slot whose value is %Object.prototype%.</li>
     </ul>
 
+    <emu-note>
+      An ECMAScript implementation that includes the ECMA-402 Internationalization API extends this prototype with additional properties in order to represent calendar data.
+    </emu-note>
+
     <emu-clause id="sec-temporal.plainmonthday.prototype.constructor">
       <h1>Temporal.PlainMonthDay.prototype.constructor</h1>
       <p>The initial value of `Temporal.PlainMonthDay.prototype.constructor` is %Temporal.PlainMonthDay%.</p>

spec/plainyearmonth.html

@@ -90,6 +90,10 @@ <h1>Properties of the Temporal.PlainYearMonth Prototype Object</h1>
       <li>has a [[Prototype]] internal slot whose value is %Object.prototype%.</li>
     </ul>
 
+    <emu-note>
+      An ECMAScript implementation that includes the ECMA-402 Internationalization API extends this prototype with additional properties in order to represent calendar data.
+    </emu-note>
+
     <emu-clause id="sec-temporal.plainyearmonth.prototype.constructor">
       <h1>Temporal.PlainYearMonth.prototype.constructor</h1>
       <p>The initial value of `Temporal.PlainYearMonth.prototype.constructor` is %Temporal.PlainYearMonth%.</p>

spec/zoneddatetime.html

@@ -93,6 +93,10 @@ <h1>Properties of the Temporal.ZonedDateTime Prototype Object</h1>
       <li>has a [[Prototype]] internal slot whose value is %Object.prototype%.</li>
     </ul>
 
+    <emu-note>
+      An ECMAScript implementation that includes the ECMA-402 Internationalization API extends this prototype with additional properties in order to represent calendar data.
+    </emu-note>
+
     <emu-clause id="sec-temporal.zoneddatetime.prototype.constructor">
       <h1>Temporal.ZonedDateTime.prototype.constructor</h1>
       <p>The initial value of `Temporal.ZonedDateTime.prototype.constructor` is %Temporal.ZonedDateTime%.</p>