[#30222] Add dateAdd method and implement
 + [#30230] JPlugin autoloadLanguage property. Thanks Elijah
Merge remote-tracking branch 'origin/master'
 # [#29319] SEF plugin gives wrong canonical url (of category, not from
article)
Merge fix for joomla/joomla-platform#1279
# [#30248] Show Intro Text = Hide currently has no effect in Featured and Category menu items.
 #$ [#29563] Error msg when an invalid back-end template is selected.
Thanks Lukas
Updated Base