v1.0.1 of hijri_core

Hijri/Gregorian calendar conversion for Dart and Flutter. Pluggable engine system with built-in Umm al-Qura and FCNA calendars. Zero dependencies. Changelog excerpt: ### Fixed - toHijrinow normalizes the input DateTimeto its UTC calendar day before lookup (via date.toUtc()), matching the UTC-midnight contract of toGregorian. Previously, passing a local DateTimeon a host west of UTC could return the previous Hijri day, breaking toHijri(toGregorian(y, m, d))round-trips. Applies to both the UAQ and FCNA engines.