v2.0.0

What's new

• Rewritten code to follow the latest PHP coding standards
• Dropped support for PHP versions earlier than 8.0
• Added new isPrivate() method
• Added new contains() method
• Fixed calculation of usable addresses for /32 and /31 IPv4 subnets
• Added unit tests
• Removed __toString() method
• Implemented JsonSerializable to support JSON serialization in the same format as the previous __toString() output