default cache-control header to 10 minutes (#1606)
default cache-control header to 10 minutes (#1606)

* default cache-control header to 10 minutes

https://cloud.google.com/appengine/docs/standard/python/config/appref

* Update app.yaml
dart-lang/dart-pad,dart-lang/dart-pad,dart-lang/dart-pad,dart-lang/dart-pad