start working on shift paring balancing

output/timetable.js

@@ -149,6 +149,8 @@ function generateExtra() {
 
             bank_holidays_worked = bank_holidays.length;
 
+            nights_worked= $(tr).find(".night-shift").length;
+
             shift_diff = JSON.parse(worker_td.attr("data-shift-diff"));
             summed_shift_diff = Object.values(shift_diff).reduce((a, b) => a + b);
 
@@ -161,6 +163,7 @@ function generateExtra() {
             worker_td.after(`<div class='worker-summary auto-generated'>
             <span>Total shifts: ${total_shifts}, </span>
             <span>Weekends: ${weekends_worked}, </span>
+            <span>Nights: ${nights_worked}, </span>
             <span>Bank holidays: ${bank_holidays_worked}, </span>
             <span class='shift-diff-span'>Summed shift diff: ${summed_shift_diff.toPrecision(2)}, </span>