Clarify translatable string in date picker

We need to clearly specify context, otherwise the translations get
messed up.
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/media/js/bootstrap-datepicker.js

@@ -1558,10 +1558,10 @@
 	var dates = $.fn.datepicker.dates = {
 		en: {
 			days: [gettext("Sunday"), gettext("Monday"), gettext("Tuesday"), gettext("Wednesday"), gettext("Thursday"), gettext("Friday"), gettext("Saturday"), gettext("Sunday")],
-			daysShort: [gettext("Sun"), gettext("Mon"), gettext("Tue"), gettext("Wed"), gettext("Thu"), gettext("Fri"), gettext("Sat"), gettext("Sun")],
-			daysMin: [gettext("Su"), gettext("Mo"), gettext("Tu"), gettext("We"), gettext("Th"), gettext("Fr"), gettext("Sa"), gettext("Su")],
+			daysShort: [pgettext("Short (eg. three letter) name of day in week", "Sun"), pgettext("Short (eg. three letter) name of day in week", "Mon"), pgettext("Short (eg. three letter) name of day in week", "Tue"), pgettext("Short (eg. three letter) name of day in week", "Wed"), pgettext("Short (eg. three letter) name of day in week", "Thu"), pgettext("Short (eg. three letter) name of day in week", "Fri"), pgettext("Short (eg. three letter) name of day in week", "Sat"), pgettext("Short (eg. three letter) name of day in week", "Sun")],
+			daysMin: [pgettext("Minimal (eg. two letter) name of day in week", "Su"), pgettext("Minimal (eg. two letter) name of day in week", "Mo"), pgettext("Minimal (eg. two letter) name of day in week", "Tu"), pgettext("Minimal (eg. two letter) name of day in week", "We"), pgettext("Minimal (eg. two letter) name of day in week", "Th"), pgettext("Minimal (eg. two letter) name of day in week", "Fr"), pgettext("Minimal (eg. two letter) name of day in week", "Sa"), pgettext("Minimal (eg. two letter) name of day in week", "Su")],
 			months: [gettext("January"), gettext("February"), gettext("March"), gettext("April"), gettext("May"), gettext("June"), gettext("July"), gettext("August"), gettext("September"), gettext("October"), gettext("November"), gettext("December")],
-			monthsShort: [gettext("Jan"), gettext("Feb"), gettext("Mar"), gettext("Apr"), gettext("May"), gettext("Jun"), gettext("Jul"), gettext("Aug"), gettext("Sep"), gettext("Oct"), gettext("Nov"), gettext("Dec")],
+			monthsShort: [pgettext("Short name of month", "Jan"), pgettext("Short name of month", "Feb"), pgettext("Short name of month", "Mar"), pgettext("Short name of month", "Apr"), pgettext("Short name of month", "May"), pgettext("Short name of month", "Jun"), pgettext("Short name of month", "Jul"), pgettext("Short name of month", "Aug"), pgettext("Short name of month", "Sep"), pgettext("Short name of month", "Oct"), pgettext("Short name of month", "Nov"), pgettext("Short name of month", "Dec")],
 			today: gettext("Today"),
 			clear: gettext("Clear"),
 			weekStart: django.formats.FIRST_DAY_OF_WEEK