How to relax Content Security Policy

That’s not a good idea. It will never work. A development environment is necessity different as it has assets precompiled and a bunch of other stuff that makes development impossible. Unless you are developing plugins you don’t need a development environment at all. So if that’s the case then you can have your development environment be a docker install, it’s just not what would be called a development environment here.

You want to launch your staging and production environments using docker as described in the standard install.