ci: pull request template includes sample format (#1357) (#172)

Source-Link: googleapis/synthtool@e122cb0
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-java:latest@sha256:387835a1375a0049ec44e02542c844302854c732d8291bdf8e472c0ff70a8f67

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,4 +13,4 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-java:latest
-  digest: sha256:3c950ed12391ebaffd1ee66d0374766a1c50144ebe6a7a0042300b2e6bb5856b
+  digest: sha256:387835a1375a0049ec44e02542c844302854c732d8291bdf8e472c0ff70a8f67

.github/PULL_REQUEST_TEMPLATE.md

@@ -5,3 +5,6 @@ Thank you for opening a Pull Request! Before submitting your PR, there are a few
 - [ ] Appropriate docs were updated (if necessary)
 
 Fixes #<issue_number_goes_here> ☕️
+
+If you write sample code, please follow the [samples format](
+https://github.com/GoogleCloudPlatform/java-docs-samples/blob/main/SAMPLE_FORMAT.md).