feat(argocd-notifications): Add slack icon and signingSecret support and Grafana support (#384)

* Add icon and signingSecret support

* Fix typo

* Add grafana support

* Fix trailing spaces

* Fix trailing spaces 2

* Fix grafana comments

* Add bot manifests

* Bump version

* No new line character

* Values.yaml new line character

* Add comments

* Add slack.enabled flag

* Move slack bot to bots/slack folder

Co-authored-by: sergeyshaykhullin <sergeyshaykhullin@gmail.com>
Co-authored-by: Sergey Shaykhullin <46970457+sergeyshaykhullin@users.noreply.github.com>

charts/argocd-notifications/templates/bots/slack/rolebinding.yaml

@@ -0,0 +1,13 @@
+{{ if .Values.bots.slack.enabled }}
+apiVersion: rbac.authorization.k8s.io/v1
+kind: RoleBinding
+metadata:
+  name: {{ include "argocd-notifications.name" . }}-bot
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: Role
+  name: {{ include "argocd-notifications.name" . }}-bot
+subjects:
+- kind: ServiceAccount
+  name: {{ include "argocd-notifications.bots.slack.serviceAccountName" . }}
+{{ end }}