new: Add i3 window manager

src/main.c

@@ -187,6 +187,12 @@ int main(int argc, char** argv, char** envp){
       .desc=_("Tiling window manager based on binary space partitioning"),
       .pkg="bspwm",
       .cmd="bspwm\n"
+    },
+    {
+      .name="i3",
+      .desc=_("Improved tiling window manager"),
+      .pkg="i3",
+      .cmd="i3\n"
     }
   };