[gtk+] docs/gtk: Include css.xml

[Rico Tzschichholz <ricotz src gnome org>]

commit e213ec9e365da323a00c3a9c8e77d28945e8ec61
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Mon Jan 4 10:16:45 2016 +0100

    docs/gtk: Include css.xml

 docs/reference/gtk/Makefile.am |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/gtk/Makefile.am b/docs/reference/gtk/Makefile.am
index eb8cd43..f02c98b 100644
--- a/docs/reference/gtk/Makefile.am
+++ b/docs/reference/gtk/Makefile.am
@@ -285,6 +285,7 @@ content_files =                                     \
        broadwayd.xml                           \
        building.sgml                           \
        compiling.sgml                          \
+       css.xml                                 \
        drawing-model.xml                       \
        getting_started.xml                     \
        glossary.xml                            \