Motivation for this change

Adding a python package to the neovim environment should not trigger a recompilation. Neovim compilation time is short but between home-manager/nixops/nixos-rebuild, it can get annoying.

This creates a neovim wrapper that just setups the correct neovim configuration (python packages/ ruby etc).

Mostly I had 2 questions:
-What should be the wrapper name for the .desktop file for instance
-recent versions of neovim allows to override the clipboard via g:clipboard, maybe it would be better to use this than patch upstream.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.