Add new template to deploy new stack in production environment

.gitlab/issue_templates/deploy-new-stack-in-production.md

+/title production: Deploy new <project> stack
+
+/milestone %<milestone>
+
+/label ~"activity::deployment"
+
+- [ ] [swh-charts](https://gitlab.softwareheritage.org/swh/infra/ci-cd/swh-charts/-/blob/production/swh/values/production.yaml?ref_type=heads#L126): Checkout production branch
+- [ ] [swh-charts](https://gitlab.softwareheritage.org/swh/infra/ci-cd/swh-charts/-/blob/production/swh/values/production.yaml?ref_type=heads#L143): Adapt values to reference the new lister and loader (equivalent to what was done for staging)
+- [ ] Deploy (push branch and let argocd do its job)
+- [ ] Tag grafana with "deployment service=loader-<project> service=<lister-project> environment=production" [1]
+- [ ] Checks pods are doing their jobs
+
+Dashboard to follow [1]
+
+[1] https://grafana.softwareheritage.org/goto/e-c3EAWIz?orgId=1
+
+Refs. <issue>