Bug 29478: Flatpickr - Restore 'Today' button

Bug 29478: Flatpickr - Restore 'Today' button

It's not implemented, looks like we need to use a plugin for that

https://github.com/flatpickr/flatpickr/issues/576

https://github.com/jcsmorais/shortcut-buttons-flatpickr

Test plan:
Confirm that flatpickr instances now have a yesterday, today and
tomorrow buttons.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>