Introduce configPath option to make mkNeovim function purer

[shofel]

Context: Updates are complicated

When kickstart-nix.nvim is used as an input in a nixos configuration, then update of neovim in a nixos system becomes a complex task:

1. update and commit the changes to neovim config
2. push
3. update the input in nixos flake
4. rebuild the flake

This flow is just too complex and labour-intensive for real life. Some strong people can stand it, i believe 💪

Proposal

1. Introduce an argument configDir to mkNeovim function
2. Expose mkNeovim function as a flake output: outputs.lib.mkNeovim

Consequences

1. one can store the neovim config directory in the same repository as nixos configuration
2. it becomes easier to integrate kickstart-nix.nvim into an existing flake:

• import mkNeovim
• then prepare the nvim config directory, and the list of plugins/externalPackages
• call mkNeovim to make a package

3. It becomes easy to use it as a non-flake (I didn't try this)

• import the mkNeovim function
• prepare the arguments
• and call the function

Progress

https://github.com/shofel/dotfiles/blob/b86ed2e5e4bb13fd6f80f6df724ddcab056c1765/neovim/neovim-overlay.nix#L140
I did actually extract the argument, but used it only with the same ./nvim directory as far

[mrcjkb]

Hey 👋

Personally, I'm quite okay with the "labour-intensive" task you describe.
Keep in mind that this is a template repo that you can fork and modify as you wish - that includes moving everything into your NixOS config repo.