Add git add interactive alias

Use gai to quickly reach interactive add mode.

git/.config/sh/alias.d/git.sh

@@ -4,6 +4,7 @@ if exist git; then
 
   alias ga='git add'
   alias gaa='git add --all'
+  alias gai='git add -i'
   alias gb='git branch'
   alias gbd='git branch -d'