Add note in README about official Nginx role

[Jeff Geerling]

See:

• https://galaxy.ansible.com/nginxinc/nginx/
• https://github.com/nginxinc/ansible-role-nginx

Nginx, Inc. now maintains and supports a pretty comprehensive Ansible role, and IMO most people should—if it meets their use case—use that role instead of mine, since it's hopefully a bit more generic, more broadly tested, and has official support behind it.

My role is basically made for one use case: my own (though I use it pretty broadly, for static webservers, for PHP servers, for reverse proxies, simple load balancers, etc.); many open PRs add features that I'd never need, therefore I'm reluctant to pull and/or maintain them, but I leave them open.

Anyways, anyone else have thoughts here? I'm thinking of adding a snippet to the top of the README mentioning the official role, and instructing people to try it out if it meets their needs.

[Jeff Geerling]

cc @alessfg