Need to allow hidden customizations

[wmertens]

people should be able to add their own configuration without committing it to this repo. Maybe import from a certain symlink if it is present?

[wmertens]

Since flakes are supposed to be fully defined, I think this is maybe not a good idea.

Instead, perhaps provide a script that sets up a private local dotfiles flake, which uses this flake as input and also provides username etc in a regular way. This solves #1 as well.

Something like

$ nix registry add dotfiles github:StratoKit/dotfiles
$ nix run dotfiles

that could run a script which looks at ~/.config/dotfiles, creates it if not exists with dotfiles as input, warns if the flake is out of date, and runs home-manager switch.