Locale selector field

Changed

• Updated Craft CMS requirement to ^5.0.0
• Replaced getContentColumnType() with static dbType() method (Craft 5 API)
• Replaced Arrayy\array_first() with native PHP reset() (voku/arrayy package removed in Craft 5)

Added

• add an "All" option to allow selecting all sites in the field settings
• add the ability to select / deselect all countries in the field settings

  Fixed

• settings now only show the country or site whitelist according to the selected datatype

Fixed

• field value is now correctly localized (for countries)

First public release. Functional but there may be glitches.