[gimp-web] Add an example for the `with-files` macro in the 2.9.4 news.

[Jehan Pagès <jehanp src gnome org>]

commit 121183066add421e3d2aec3a966efade20e9d019
Author: Jehan <jehan girinstud io>
Date:   Tue Jul 12 22:41:33 2016 +0200

    Add an example for the `with-files` macro in the 2.9.4 news.

 .../news/2016-06-02 GIMP 2.9.4 Released/index.md   |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/content/news/2016-06-02 GIMP 2.9.4 Released/index.md b/content/news/2016-06-02 GIMP 2.9.4 
Released/index.md
index 946dedb..3f24a6e 100644
--- a/content/news/2016-06-02 GIMP 2.9.4 Released/index.md      
+++ b/content/news/2016-06-02 GIMP 2.9.4 Released/index.md      
@@ -126,6 +126,15 @@ The _Text_ tool now fully supports advanced input methods for CJK and other non-
 
 A new macro `with-files` is now available in order to easily process multiple files through GIMP, on command 
line, which was a much awaited feature.
 
+For instance, if you wanted to invert colors of all PNG images from the current folder, then save them as 
JPEG, you could run from the command line:
+
+```bash
+gimp -i -b '(with-files "*.png" (gimp-invert layer) \
+             (gimp-file-save 1 image layer \
+              (string-append basename ".jpg") \
+              (string-append basename ".jpg") ))'
+```
+
 ## Email plugin back from the dead
 
 The `File > Send by email…` dialog will open your default email client with an attached copy of your current 
image, to share your work-in-progress in a single click. This is available only on operating systems with 
`xdg-email` (likely GNU/Linux, BSD only).