refactor(flake): split NixOS Home Manager configs

Create a NixOS-specific Home Manager configuration and a reusable shared
configuration that can be imported and also used by other configurations,
such as WSL2.

system/shared/home-manager-packages.nix

@@ -0,0 +1,53 @@
+{ inputs, pkgs, ... }:
+
+with pkgs; [
+  awscli2
+  bottom
+  ctop
+  delta
+  dog
+  doppler
+  exa
+  fd
+  file
+  fzf
+  gcc
+  gh
+  git
+  git-crypt
+  gnupg
+  htop
+  inotify-tools
+  inputs.nixpkgs-unstable.legacyPackages."${system}".rustywind
+  jq
+  just
+  lua
+  mysql
+  neofetch
+  nodePackages."http-server"
+  nodePackages.eslint
+  nodePackages.nodemon
+  nodePackages.prettier
+  nodejs
+  php81
+  php81Packages.composer
+  php81Packages.phpcbf
+  php81Packages.phpcs
+  php81Packages.phpstan
+  platformsh
+  pulumi-bin
+  pv
+  python3Full
+  ripgrep
+  terraform
+  tldr
+  tmuxinator
+  tree
+  tree-sitter
+  unzip
+  virtualenv
+  wget
+  xcp
+  xh
+  yarn
+]