[chore] add helm chart update task to PR template (#855)

* add helm chart update task

Signed-off-by: Pierre Tessier <pierre@pierretessier.com>

* fix link reference

Signed-off-by: Pierre Tessier <pierre@pierretessier.com>

---------

Signed-off-by: Pierre Tessier <pierre@pierretessier.com>

Author: puckpuck

.github/PULL_REQUEST_TEMPLATE.md

@@ -9,9 +9,22 @@ essential items:
 
 * [ ] `CHANGELOG.md` updated to document new feature additions
 * [ ] Appropriate documentation updates in the [docs][]
+* [ ] Appropriate Helm chart updates in the [helm-charts][]
+
+<!--
+A Pull Request that modifies instrumentation code will likely require an
+update in docs. Please make sure to update the opentelemetry.io repo with any
+docs changes.
+
+A Pull Request that modifies docker-compose.yaml, otelcol-config.yaml, or
+Grafana dashboards, will likely require an update to the Demo Helm chart.
+Other changes affecting how a service is deployed will also likely require an
+update to the Demo Helm chart.
+-->
 
 Maintainers will not merge until the above have been completed. If you're unsure
 which docs need to be changed ping the
 [@open-telemetry/demo-approvers](https://github.com/orgs/open-telemetry/teams/demo-approvers).
 
 [docs]: https://opentelemetry.io/docs/demo/
+[helm-charts]: https://github.com/open-telemetry/opentelemetry-helm-charts