add a webmaster tools verification file (#3902)

* add a webmaster tools verification file

* also put the verification file at the root of our bucket

* add comment for when we can simplify this script

dev/docs/google2ed1af765c529f57.html

+google-site-verification: google2ed1af765c529f57.html
\ No newline at end of file

infra/docs.sh

@@ -8,7 +8,12 @@ pub global activate dartdoc
 (cd dev/tools; pub get)
 dart dev/tools/dartdoc.dart
 
+cp dev/docs/google2ed1af765c529f57.html dev/docs/doc/api
+
 # Upload the docs.
 if [ "$1" = "--upload" ]; then
+  # TODO: delete this line when we publish our API docs into the
+  # root of the bucket
+  gsutil cp dev/docs/google2ed1af765c529f57.html gs://docs.flutter.io
   gsutil -m rsync -d -r dev/docs/doc/api gs://docs.flutter.io/flutter
 fi