Add CONTRIBUTING.md
Add CONTRIBUTING.md

lazyfrosch/puppet-icinga2,Icinga/puppet-icinga2,lazyfrosch/puppet-icinga2,Icinga/puppet-icinga2,lazyfrosch/puppet-icinga2,Icinga/puppet-icinga2-rewrite,Icinga/puppet-icinga2-rewrite,Icinga/puppet-icinga2-rewrite