feat: Shortcut to nix config

So that we're able to do `darwin-rebuild --flake .` since there's no
default flake path at the moment. There's however a PR that'll set
nix-darwin default flake path to `~/.config/nix-darwin` (or
`/etc/nix-darwin`).

REF:
 - LnL7/nix-darwin#721
 - LnL7/nix-darwin#741

.config/zsh/include/aliases

@@ -76,7 +76,8 @@ alias reUSD='rm -rf /tmp/rate.html /tmp/rateUSD.txt'
 #alias mpv='mpv --geometry=1280x720'
 
 #config shortcuts
-alias config='cd ${DOTFILES:-$HOME/Build/GIT/dotfiles}'
+alias cdnix="cd $XDG_CONFIG_HOME/nix"
+alias config="cd ${DOTFILES:-$HOME/Build/GIT/dotfiles}"
 alias cfg='config'
 alias cfvim='vim $XDG_CONFIG_HOME/nvim/init.lua'
 alias cfvimplug='vim $XDG_CONFIG_HOME/nvim/lua/null/plugins/'