Show calendar week number

[TauPan]

e.g. something like ' 2021 / November 15 - 21 - Week 46' in the title of the week view.

Or similar to calendar-intermonth-text set to

(propertize
 (format "%2d"
         (car
          (calendar-iso-from-absolute
           (calendar-absolute-from-gregorian
            (list month day year)))))
 'font-lock-face 'calendar-iso-week-face)

Which displays the week number in front of the days row.

Example M-x calendar result without font locking:

        September 2021            October 2021            November 2021    
  KW Mo Tu We Th Fr Sa Su  KW Mo Tu We Th Fr Sa Su  KW Mo Tu We Th Fr Sa Su 
  35        1  2  3  4  5  39              1  2  3  44  1  2  3  4  5  6  7 
  36  6  7  8  9 10 11 12  40  4  5  6  7  8  9 10  45  8  9 10 11 12 13 14 
  37 13 14 15 16 17 18 19  41 11 12 13 14 15 16 17  46 15 16 17 18 19 20 21 
  38 20 21 22 23 24 25 26  42 18 19 20 21 22 23 24  47 22 23 24 25 26 27 28 
  39 27 28 29 30           43 25 26 27 28 29 30 31  48 29 30