Add flux create secret receiver command

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

cmd/flux/testdata/create_secret/receiver/secret-receiver.yaml

@@ -0,0 +1,11 @@
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  annotations:
+    notification.toolkit.fluxcd.io/webhook: https://flux.example.com/hook/106120121d366c2f67e93200f6c1dbe938235eb588daa5e8c0516d3a77ac1dee
+  name: receiver-secret
+  namespace: my-namespace
+stringData:
+  token: test-token
+