[devhelp] NEWS file: add news in 3.28.1

[Sébastien Wilmet <swilmet src gnome org>]

commit 64e41d7d851bd7283d1c83180b15727d02b5832e
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Apr 8 12:07:29 2018 +0200

    NEWS file: add news in 3.28.1

 NEWS |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/NEWS b/NEWS
index 17ed280..8abf46b 100644
--- a/NEWS
+++ b/NEWS
@@ -4,10 +4,14 @@ News in 3.29.1, 2018-xx-yy (not yet released)
   files needed to be split in two.
 * Switch build system from Autotools to Meson (and remove Autotools).
 * Update the license from GPLv2+ to GPLv3+.
-* AppData: update screenshots.
 * A few other small improvements.
 * Translation updates.
 
+News in 3.28.1, 2018-04-08
+--------------------------
+* AppData: update screenshots.
+* Translation updates.
+
 News in 3.28.0, 2018-03-10
 --------------------------
 * Improve default GSettings values.