Add new date format tokens for weekday number

See https://en.wikipedia.org/wiki/ISO_8601#Week_dates

core/modules/utils/utils.js

@@ -383,6 +383,9 @@ exports.formatDateString = function(date,template) {
 			[/^0WW/, function() {
 				return $tw.utils.pad($tw.utils.getWeek(date));
 			}],
+			[/^dddd/, function() {
+				return [7,1,2,3,4,5,6][date.getDay()];
+			}],
 			[/^ddd/, function() {
 				return $tw.language.getString("Date/Short/Day/" + date.getDay());
 			}],

editions/tw5.com/tiddlers/features/DateFormat.tid

@@ -1,5 +1,5 @@
 created: 20140418142957325
-modified: 20201201154521138
+modified: 20210912115121622
 tags: Features
 title: DateFormat
 type: text/vnd.tiddlywiki
@@ -9,6 +9,7 @@ When used to display date values (with the `format` attribute set to ''date''),
 |!Token |!Substituted Value |
 |`DDD` |Day of week in full (eg, "Monday") |
 |`ddd` |Short day of week (eg, "Mon") |
+|`dddd` |<<.from-version "5.2.0">> Weekday number from 1 through 7, beginning with Monday and ending with Sunday |
 |`DD` |Day of month |
 |`0DD` |Adds a leading zero |
 |`DDth` |Adds a suffix |