I had to export the Calendar type from Season to use it from
campsite/types, and also renamed them because season.SeasonCalendar is
a bit redundant compared to just season.Calendar.
I still have not added the HTMx code to switch year because i am not
sure whether Oriol will want to show a whole year or just half a year.
The calculation for the text color taking into account the contrast with
the background is from [0].
[0]: https://www.smashingmagazine.com/2020/07/css-techniques-legibility/#foreground-contrast