Make an issue template for updating all application components

Template should be something like this:

* [ ] Docker image
* [ ] requirements.txt (#674)
* [ ] mitogen (see https://github.com/mitogen-hq/mitogen/issues/731 for ansible 2.10 support)
* [ ] k3s (beware of #654)
* [ ] helm
* [ ] krew
* [ ] Update chart API versions 

Installed by flux:

* [ ] ./kube-system/metallb.yaml
* [ ] ./kube-system/local-path-provisioner.yaml
* [ ] ./oas/grafana.yaml
* [ ] ./oas/letsencrypt-production.yaml
* [ ] ./oas/single-sign-on.yaml
* [ ] ./oas/prometheus.yaml
* [ ] ./oas/letsencrypt-staging.yaml
* [ ] ./oas/ingress.yaml
* [ ] ./oas/loki-stack.yaml (#683)
* [ ] ./velero/velero.yaml
* [ ] ./oas-custom/flux-custom.yaml
* [ ] ./cert-manager/cert-manager.yaml
* [ ] ./oas-apps/nextcloud.yaml (https://open.greenhost.net/openappstack/nextcloud/-/issues/38)
* [ ] ./oas-apps/wordpress.yaml
* [ ] ./oas-apps/rocketchat.yaml (#647, #589)


Existing issues for other components: 

* [flux2](https://open.greenhost.net/openappstack/openappstack/-/issues/677)
* [Use loki + promtail charts instead of loki-stack](https://open.greenhost.net/openappstack/openappstack/-/issues/683)

(from #691 (closed))