[gnome-builder] doc: add blurb on fullscreen

[Christian Hergert <chergert src gnome org>]

commit e6cfa9df85d6563720dcceed34ef3141994852e2
Author: Christian Hergert <chergert redhat com>
Date:   Thu Sep 7 00:54:46 2017 -0700

    doc: add blurb on fullscreen

 doc/exploring.rst |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/doc/exploring.rst b/doc/exploring.rst
index 235f35d..aa819e4 100644
--- a/doc/exploring.rst
+++ b/doc/exploring.rst
@@ -92,6 +92,8 @@ You can move them out of the way using the buttons in the top left of the workbe
    :width: 133 px
    :align: center
 
+When entering Fullscreen mode, Builder will automatically dismiss the panels for your convenience.
+
 Additionally, you can use the "left-visible" or "bottom-visible" commands from the `Command Bar`_ to toggle 
their visibility.
 
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