Version 0.7.2

• Add preliminary PHP 8.1 support. #109
  • Extensions should now compile for PHP 8.1. This doesn't implement any of the
    new PHP 8.1 features.
• Add anyhow cargo feature to implement
  From<anyhow::Error> for PhpException. #110
• Made ClassMetadata: Send + Sync. #111
• Fixed registering constants with expressions. #112