Bug 34440: Add handling for lead/trail display

Bug 34440: Add handling for lead/trail display

This patch adds code to insert classes into the flatpickr for lead and
trail time on bookings and includes some scss additions to highlight
said periods in display.

Sponsored-by: Cuyahoga County Public Library <https://cuyahogalibrary.org/>
Signed-off-by: Kristi Krueger <KKRUEGER@cuyahogalibrary.org>
Signed-off-by: Paul Derscheid <paul.derscheid@lmscloud.de>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>