testing the hook reveals it is called before customize-image.sh (pr…

…oper sentence) (#351)

* testing the hook reveals it is called before `customize-image.sh` (proper english this time)

Mixed before and after in documentation of the hook. (if it can be used the same way as `customize-image.sh` will be tested tomorrow, i think if the image is not mounted, you cant do system settings)

* As it is triggered before mounting the overlay, it cannot be used exactly like the `customize-image.sh`

As it is triggered before mounting the overlay, it cannot be used exactly like the `customize-image.sh`

docs/Developer-Guide_Extensions-Hooks.md

@@ -105,8 +105,8 @@ access to the rootfs (`${SDCARD}`) in its pristine state after packages are inst
 
 > *run before customize-image.sh*
 
-This hook is called after `customize-image.sh` is called, but before the overlay is mounted. It thus can be used
-for the same purposes as `customize-image.sh`.
+This hook is called before `customize-image.sh` is executed and before the overlay is mounted. It thus can be used
+for the same purposes as `customize-image.sh` without the overlay.
 
 Also known as (for backwards compatibility only):