Editorial: Add two more required formats

This makes format selection in BasicFormatMatcher unambiguous when
requesting the following two formats:

1. Standalone "month":

There's currently a tie between "year, month" and "month, day". Adding
standalone "month" as a required format resolves this tie.

2. "dayPeriod, hour, minute, second, fractionalSecondDigits":

There's a tie between "hour, minute, second, fractionalSecondDigits" and
"dayPeriod, hour, minute, second". Requiring a format which has both
"dayPeriod" and "fractionalSecondDigits" resolves this tie.

Author: anba

spec/datetimeformat.html

@@ -247,12 +247,14 @@ <h1>Internal slots</h1>
             <li>year, month, day</li>
             <li>year, month</li>
             <li>month, day</li>
+            <li>month</li>
             <li>hour, minute, second, fractionalSecondDigits</li>
             <li>hour, minute, second</li>
             <li>hour, minute</li>
-            <li>dayPeriod, hour</li>
+            <li>dayPeriod, hour, minute, second, fractionalSecondDigits</li>
             <li>dayPeriod, hour, minute, second</li>
             <li>dayPeriod, hour, minute</li>
+            <li>dayPeriod, hour</li>
           </ul>
         </li>
         <li>