add basic customizations

[anuaimi]

here is what timeanddate offers. It's clearly too much but should be reviewed to see if there are any that would be of interest to large groups of people

https://www.timeanddate.com/calendar/custommenu.html

possibilities include:

• country official holidays (need to choose country)
• language (other than English)
• key moon phases
• days left in the year (as percent?)
• what 1st day of the week is (which countries don't have Monday as the 1st day of the year)