[libgxps] Add .gitattributes file to not inckude regstest dir in tarballs

[Carlos Garcia Campos <carlosgc src gnome org>]

commit a33fef2f30611d4c2e402dcc0593ff01a5960d0e
Author: Carlos Garcia Campos <carlosgc gnome org>
Date:   Wed Aug 9 11:33:24 2017 +0200

    Add .gitattributes file to not inckude regstest dir in tarballs

 .gitattributes |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..b95576d
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,2 @@
+.gitattributes export-ignore
+regtest export-ignore