[atk] NEWS: added missing Contributors on past releases

[Alejandro Piñeiro Iglesias <apinheiro src gnome org>]

commit 3dbaec56dd6bef2f1a521a9970b99193481a4f3f
Author: Alejandro Piñeiro <apinheiro igalia com>
Date:   Wed Apr 25 08:31:21 2018 +0200

    NEWS: added missing Contributors on past releases

 NEWS |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/NEWS b/NEWS
index 9123f27..f04549d 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,9 @@ Changes in version 2.28
 * documentation
    * Bug 791020: Remove list association from ATK_ROLE_DESCRIPTION_{TERM,VALUE}
 
+Contributors:
+ Joanmarie Diggs
+
 Translations
  Claude Paroz (fr), GNOME Translation Robot (gd)
 
@@ -22,6 +25,9 @@ Changes in version 2.27.1
 * Build (Visual Studio)
    * Enhance security of x64 binaries
 
+Contributors
+  Chun-wei Fan
+
 Translations
   Pawan Chitrakar (ne), Xavi Ivars (ca@valencia), hanniedu (nl)