feat(nix): add zellij

Signed-off-by: Seongmin Lee <[e-mail]>

nix/flake.nix

···
         pkgs.ripgrep
         pkgs.sumneko-lua-language-server
         pkgs.unixtools.watch
+        pkgs.zellij
         pkgs-unstable.jujutsu
         pkgs-unstable.neovim
       ] ++ (if pkgs.stdenv.isDarwin then [

zsh/.zshrc

···
 alias ta="tmux attach"
 alias nn="NVIM_APPNAME=nativevim nvim"
 alias nd="nix develop -c zsh -l"
+alias zj="zellij"
 
 ## Custom prompt
 setopt prompt_subst