Create detailed documentation and improve support for Xdebug

[jaydrogers]

👉 Describe the problem

Some users rely on Xdebug and there are extra steps involved to get it to work.

👥 Problem evidence & reach

• Xdebug with fpm-nginx #176

🏆 How to solve this problem

• Create documentation how to set this up in development
• Possibly make it easier by providing a standardized INI file that can easily be enabled

🥰 Describe the "impact" on users?

It will dramatically reduce the headache and effort for configuring Xdebug with PHP + Docker.

💯 How do we validate the problem is solved?

• Steps are clearly documented how to enable Xdebug
• Xdebug can easily work in development, but it does not run in production