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

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

README.md

@@ -69,6 +69,7 @@ For provisioning the following tools will be used:
 | [go-task](https://github.com/go-task/task)         | A task runner / simpler Make alternative written in Go                                                                                  |
 | [ipcalc](http://jodies.de/ipcalc)                  | Used to verify settings in the configure script                                                                                         |
 | [jq](https://stedolan.github.io/jq/)               | Used to verify settings in the configure script                                                                                         |
+| [yq](https://github.com/mikefarah/yq)              | Used to verify settings in the configure script                                                                                         |
 | [kubectl](https://kubernetes.io/docs/tasks/tools/) | Allows you to run commands against Kubernetes clusters                                                                                  |
 | [sops](https://github.com/mozilla/sops)            | Encrypts k8s secrets with Age                                                                                                           |
 | [terraform](https://www.terraform.io)              | Prepare a Cloudflare domain to be used with the cluster                                                                                 |
@@ -337,6 +338,36 @@ To access services from the outside world port forwarded `80` and `443` in your
 
 Now if nothing is working, that is expected. This is DNS after all!
 
+### 🪝 Github Webhook
+
+Flux is pull-based by design meaning it will periodically check your git repository for changes, using a webhook you can enable Flux to update your cluster on `git push`. In order to configure Github to send `push` events from your repository to the Flux webhook receiver you will need two things:
+
+1. Webhook URL
+    Your webhook receiver will be deployed on `https://flux-receiver.${BOOTSTRAP_CLOUDFLARE_DOMAIN}/hook/:hookId`. In order to find out your hook id you can run the following command:
+
+    ```sh
+    kubectl -n flux-system get receiver/github-receiver --kubeconfig=./provision/kubeconfig
+    # NAME              AGE    READY   STATUS
+    # github-receiver   6h8m   True    Receiver initialized with URL: /hook/12ebd1e363c641dc3c2e430ecf3cee2b3c7a5ac9e1234506f6f5f3ce1230e123
+    ```
+
+    So if my domain was `k8s-at-home.com` the full url would look like this:
+
+    ```text
+    https://flux-receiver.k8s-at-home.com/hook/12ebd1e363c641dc3c2e430ecf3cee2b3c7a5ac9e1234506f6f5f3ce1230e123
+    ```
+
+2. Webhook secret
+    Your webhook secret can be found by decrypting the `secret.sops.yaml` using the following command:
+
+    ```sh
+    sops -d ./cluster/apps/flux-system/webhooks/github/secret.sops.yaml | yq .stringData.token
+    ```
+
+    **Note:** Don't forget to update the `BOOTSTRAP_FLUX_GITHUB_WEBHOOK_SECRET` variable in your `.config.env` file so it matches the generated secret if applicable
+
+Now that you have the webhook url and secret, it's time to set everything up on the Github repository side. Navigate to the settings of your repository on Github, under "Settings/Webhooks" press the "Add webhook" button. Fill in the webhook url and your secret.
+
 ### 👉 Troubleshooting
 
 Our [wiki](https://github.com/k8s-at-home/template-cluster-k3s/wiki) (WIP, contributions welcome) is a good place to start troubleshooting issues. If that doesn't cover your issue, come join and say Hi in our [Discord](https://discord.gg/k8s-at-home) server by starting a new thread in the #kubernetes support channel.