alias: Add a cal alias to bring back old behavior

As the `cal` binary changed it's behavior so that it does not
highlight the current day anymore, use `ncal -b` as a replacement.

.zshenv

@@ -30,6 +30,7 @@ alias gwc='git ls-files | xargs cat | wc'
 alias c2pdf='enscript -r -2 --highlight=c --line-numbers -o - $(git ls-files | grep -v .png | grep -v .xcf | grep -v .map) | ps2pdf -'
 alias feh='feh -FZ'
 alias white='i3lock'
+alias cal='ncal -b'
 
 #
 # Shortcuts