IsoCode.fromJson throws String instead of Exception, causing type safety issues

[ibmkynl]

throw 'Iso code not found $isoCodeStr ';

Location: https://github.com/cedvdb/phone_numbers_parser/blob/main/lib/src/iso_codes/iso_code.dart

The IsoCode.fromJson method in iso_code.dart throws a raw String instead of a proper Exception or Error object, which violates Dart best practices and causes type safety issues.

[cedvdb]

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