Drop dependency "xdan-datetimepicker-rails"

[workgena]

Background

Currently "active_admin_datetimepicker" has strong dependency on shekibobo/xdan-datetimepicker-rails

It provides Rails-wrapper for xdan/datetimepicker JS-library.

xdan-datetimepicker-rails is abandoned and is not updates since 2016.

The last update for xdan/datetimepicker JS-lib is dated 2020 year.

Proposition

Remove dependency on "shekibobo/xdan-datetimepicker-rails" and be dependant directly to "xdan/datetimepicker".

Or, create PR with update to xdan-datetimepicker-rails.

Related issues

• #68

[senid231]

i think we should just remove dependency, write instruction about how to install it via webpacker/sprockets and release major version (because it's a breaking change)