Added diff --cached aliases

diff --cached will show the diff of files I have already staged

git/git.zsh

@@ -5,6 +5,7 @@ alias gb='git branch'
 alias gl='git pull'
 alias gp='git push'
 alias gd='git diff'
+alias gdc='git diff --cached'
 alias gs='git s'
 alias gss='git stash save'
 alias gsp='git stash pop'