Add new template to deploy a stack version update

We usually do both staging then production environment when no issues arise in staging.

.gitlab/issue_templates/deploy-new-stack-version.md

+/title Deploy new <project> <version>
+
+/milestone %<milestone>
+
+/label ~"activity::deployment"
+
+staging:
+- [ ] [swh-apps](https://gitlab.softwareheritage.org/swh/infra/swh-apps/-/tree/master/apps?ref_type=heads): Build image (if required because of new deps for example)
+- [ ] [swh-charts](https://gitlab.softwareheritage.org/swh/infra/ci-cd/swh-charts/-/merge_requests): Merge MR with image versions updates triggered by the CI
+- [ ] Push branch 'staging' && Let argocd deploy and do its job
+- [ ] Checks pods are doing their jobs without crashing
+- [ ] Tag grafana with "deployment service=<service> service=<service2> ... environment=staging" [1] [2]
+
+production:
+- [ ] Merge 'staging' branch into 'production' (it should/must be a fast-forward)
+- [ ] Push branch 'production' && Let argocd deploy and do its job
+- [ ] Checks pods are doing their jobs without crashing
+- [ ] Tag grafana with "deployment service=<service> service=<service2> ... environment=production" [1] [2]
+
+[1] https://grafana.softwareheritage.org/goto/e-c3EAWIz?orgId=1
+
+[2] Only reference impacted services (e.g. storage, lister-cran, loader-git, scheduler, vault, ...)
+
+Refs. <issue>