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

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

.config.sample.env

@@ -5,6 +5,11 @@
 # The repo you created from this template
 # e.g. https://github.com/k8s-at-home/home-cluster
 export BOOTSTRAP_GIT_REPOSITORY=""
+# To enable Flux to update your cluster on `git push` set the following to one of:
+# `ignored` - this feature will be disabled
+# `generated` - this will generate a token and print it in the logs
+# Set this to any other string and it will be used for the secret
+export BOOTSTRAP_FLUX_GITHUB_WEBHOOK_SECRET="ignored"
 # Choose one of your cloudflare domains
 # e.g. k8s-at-home.com
 export BOOTSTRAP_CLOUDFLARE_DOMAIN=""