Improve developer experience with new apps

[jelhan]

If used together with Ember Auto Import manual configuration is needed. Documentation is provided in our readme.

Ember Auto Import is included in Ember CLI blueprints. This causes new projects to violate default CSP.

One solution is to change default values for configuration of Ember Auto Import. forbidEval could default to true if ember-cli-content-security-policy is present. embroider-build/ember-auto-import#345 Let's see if maintainers are open to such a change.

If not we may want to add a build time warning to improve developer experience.

[jelhan]

Closing as duplicate of #159. Ups. 🙈