Add templates and logic to set up manifests for Github webhook receiver (#308)

Co-authored-by: Devin Buhl <onedr0p@users.noreply.github.com>

tmpl/cluster/flux-system/webhooks/github/receiver.yaml

@@ -0,0 +1,43 @@
+---
+apiVersion: notification.toolkit.fluxcd.io/v1beta1
+kind: Receiver
+metadata:
+  name: github-receiver
+  namespace: flux-system
+spec:
+  type: github
+  events:
+    - ping
+    - push
+  secretRef:
+    name: github-webhook-secret
+  resources:
+    - apiVersion: source.toolkit.fluxcd.io/v1beta2
+      kind: GitRepository
+      name: flux-system
+      namespace: flux-system
+
+    - apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+      kind: Kustomization
+      name: apps
+      namespace: flux-system
+
+    - apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+      kind: Kustomization
+      name: core
+      namespace: flux-system
+
+    - apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+      kind: Kustomization
+      name: crds
+      namespace: flux-system
+
+    - apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+      kind: Kustomization
+      name: flux-system
+      namespace: flux-system
+
+    - apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
+      kind: Kustomization
+      name: traefik-crds
+      namespace: flux-system