Add RepositoryStorage example doc
Part of https://gitlab.com/gitlab-org/quality/testcases/issues/254
Forgot to include in https://gitlab.com/gitlab-org/gitlab-qa/merge_requests/347
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Part of https://gitlab.com/gitlab-org/quality/testcases/issues/254
Forgot to include in https://gitlab.com/gitlab-org/gitlab-qa/merge_requests/347