[retro-gtk] Add .gitattributes

[Adrien Plazas <aplazas src gnome org>]

commit 151dc07441ee1b56305a6e416f2b8baacecaf75a
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Sat Jun 16 14:33:35 2018 +0200

    Add .gitattributes
    
    Declares files to exclude from the archives generated by `git archive`.
    
    This will allow to exclude files when generating tarballs manually to
    compensate the lack og file exclusion of the Meson dist mechanism.

 .gitattributes | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..9515e6c
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,5 @@
+flatpak export-ignore
+.editorconfig export-ignore
+.gitattributes export-ignore
+.gitignore export-ignore
+.gitlab-ci.yml export-ignore