Added docs for `DatePicker`, `DatePickerInput` and `DatesProvider`

[AnnMarieW]

Added docs for DatePicker, DatePickerInput and DatesProvider

I created a separate PR because I think these components may take longer to review and I didn't want to hold up #36

Breaking changes (not a complete list):

• DatePickerRange component removed, use DatePickerInput with `type="range"
• DatePicker component is just the calendar now. Use DatPickerInput when migrating from previous versions.
• use datesProvider to set locale
  • inputFormat prop renamed to valueFormat
  • amountOfMonths prop was renamed to numberOfColumns in all components
  • clearable=False is now the default in DatePickerInput

Bugs:

• Need a better error message if using type="multiple" and the value is not a list. Currently the error message is "t.map is not a function"

• locale prop only works in the DatesProvider and not in DatePicker or DatePickerInput

• Missing props

  • defaultDate - Sets calendar to a date other than current date. See the example docs.datepicker.min_max

  • defaultLevel. There is level prop but no defaultLevel prop. Level doesn't work as in the docs: https://v6.mantine.dev/dates/date-picker/#default-level. See the example docs.datepicker.default_level

[snehilvj]

Thanks again @AnnMarieW