Change DROPIN_ROOT via the CLI

[vulc41n]

Is your feature request related to a problem? Please describe.
Some people, even devs, are not familiar with environment variables.

Describe the solution you'd like
It would be more accessible to change this kind of settings via the interactive CLI. I guess the process could be :

1. Launch the interactive CLI
2. Go to settings, where some other specific preferences could be managed as well
3. Go to root directory
4. Where should your recipes be stored? is prompted, the user give the path
5. The root directory is moved
6. The root directory is moved to {path}
7. We have detected you're using bash/fish/zsh/windows/..., do you want to add your configuration to your .bashrc/config.fish/...? is prompted, the user can select "Yes" or "No"
8. If "No" is selected, we prompt the generated configuration so the user can add it himself
9. Fallback to the settings section

Describe alternatives you've considered
Feel free to suggest other flow / prompts

Additional context
This feature is definitely not the most urgent one, so we won't implement it until we have a MVP, unless someone needs it.