Add pubspec.yaml to keep pub happy

Change-Id: Ia406cc91dcdca8891b3b78ce731766fba1fa0c24

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
new file mode 100644
index 0000000..13aa81c
--- /dev/null
+++ b/pubspec.yaml
@@ -0,0 +1,5 @@
+name: flutter_gallery_assets
+description: Images and fonts for the Flutter gallery demo
+version: 0.0.22
+author: Flutter Authors <flutter-dev@googlegroups.com>
+homepage: http://flutter.io