Adjust the PR template to include signing off the commits

Summary

[x] Categorize the PR by setting a good title and adding one of the labels: bug, enhancement, documentation, change, breaking, dependency as they show up in the changelog
[x] PR contains the label area:operator
[ ] Link this PR to related issues
[x] I have not made any changes in the charts/ directory.

[ ] Categorize the PR by setting a good title and adding one of the labels: bug, enhancement, documentation, change, breaking, dependency as they show up in the changelog
[ ] PR contains the label area:chart
[ ] PR contains the chart label, e.g. chart:k8up
[ ] Variables are documented in the values.yaml using the format required by Helm-Docs.
[ ] Chart Version bumped if immediate release after merging is planned
[ ] I have run make chart-docs
[ ] Link this PR to related code release or other issues.