docs(argocd-notifications): Use helm-docs (#1015)

* docs(argocd-notifications): Use helm-docs

Signed-off-by: Marco Kilchhofer <mkilchhofer@users.noreply.github.com>

* Use chart appVersion as default image tag

Signed-off-by: Marco Kilchhofer <mkilchhofer@users.noreply.github.com>

charts/argocd-notifications/README.md.gotmpl

@@ -0,0 +1,45 @@
+## ArgoCD Notifications Chart
+
+This is a **community maintained** chart. It installs the [argocd-notifications](https://github.com/argoproj-labs/argocd-notifications) application. This application comes packaged with:
+- Notifications Controller Deployment
+- Notifications Controller ConfigMap
+- Notifications Controller Secret
+- Service Account
+- Roles
+- Role Bindings
+
+To regenerate this document, from the root of this chart directory run:
+
+```console
+docker run --rm --volume "$(pwd):/helm-docs" -u $(id -u) jnorwood/helm-docs:latest
+```
+
+## Values
+
+### General parameters
+
+| Key | Type | Default | Description |
+|-----|------|---------|-------------|
+{{- range .Values }}
+  {{- if not (hasPrefix "bots" .Key) }}
+| {{ .Key }} | {{ .Type }} | {{ if .Default }}{{ .Default }}{{ else }}{{ .AutoDefault }}{{ end }} | {{ if .Description }}{{ .Description }}{{ else }}{{ .AutoDescription }}{{ end }} |
+  {{- end }}
+{{- end }}
+
+### Bots
+
+| Key | Type | Default | Description |
+|-----|------|---------|-------------|
+{{- range .Values }}
+  {{- if hasPrefix "bots" .Key }}
+| {{ .Key }} | {{ .Type }} | {{ if .Default }}{{ .Default }}{{ else }}{{ .AutoDefault }}{{ end }} | {{ if .Description }}{{ .Description }}{{ else }}{{ .AutoDescription }}{{ end }} |
+  {{- end }}
+{{- end }}
+
+----------------------------------------------
+Autogenerated from chart metadata using [helm-docs](https://github.com/norwoodj/helm-docs)
+
+[affinity]: https://kubernetes.io/docs/concepts/configuration/assign-pod-node/
+[Node selector]: https://kubernetes.io/docs/user-guide/node-selection/
+[Tolerations]: https://kubernetes.io/docs/concepts/configuration/taint-and-toleration/
+[values.yaml]: values.yaml