[gnome-session/wip/benzea/systemd-user-switch] NEWS: Add information about the new systemd user instance support

[Benjamin Berg <bberg src gnome org>]

commit 697d376b16b3bfaf8c5bde46e6feccd04a0d6363
Author: Benjamin Berg <bberg redhat com>
Date:   Fri Aug 2 13:48:00 2019 +0200

    NEWS: Add information about the new systemd user instance support

 NEWS | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
---
diff --git a/NEWS b/NEWS
index d2b980ab..6b306dda 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,17 @@
+===============
+Version 3.33.90
+===============
+       * Add support to manage the session using the systemd user instance.
+         A new systemd_session build time option is added to enable/disable
+         the support and set it as the default (disable/enable/default).
+         Right now the support is enabled by default. Distributions should
+         be careful to ensure that other components are updated at the same
+         time (gnome-settings-daemon, gnome-shell, gdm) as subtle errors
+         may occur otherwise.
+         If in doubt, only enable the feature and test it by modifying the
+         gnome-session launch script to pass --systemd to
+         gnome-session-binary.
+
 ===============
 Version 3.33.4
 ===============