Allow installing Nix without editing `/etc/bashrc` or `/etc/zshrc`

[dancojocaru2000]

Platform

• Linux:
• macOS
• WSL

Additional information

I use fish so those changes don't affect me anyway, and I don't like unnecessary changes to system files.

Checklist

• checked [latest Nix manual] ([source])
• checked [open installer issues and pull requests] for possible duplicates

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[Mic92]

Sounds like an acceptable patch to our installer.

[devatbosch]

Hi @dancojocaru2000 ,

I would like to work on this issue. Would be pretty helpful if you give a little context of this issue, On an overall sense

Thank You!