Feature-request: move to date-fns instead of dayjs/abjstract out the date functionality to a different package

[worthy7]

Current dayjs is not ESM, so it cannot be tree-shaken.

After much deliberation myself using Luxon, moment, dayjs and date-fns, in the end I went with date-fns.

You could abstract angular-datepickers date functions into a separate package - an adapter, just like how material angular works - and this would mean people can install the package they want to use with this datepicker. Thanks!