Add support for composer-plugin-api version 2

[tkoop]

When I run the composer install command, I get this message:

 [InvalidArgumentException]                                                                                                                            
  Package davidepastore/composer-audit at version 0.1.* has a PHP requirement incompatible with your PHP version, PHP extensions and Composer version:  
    - davidepastore/composer-audit v0.1.0 requires composer-plugin-api 1.0.0 which does not match your installed version 2.1.0.