Doc: Fix tilt up issue in feature discovering in developer guide

The issue is due to the k3d/kind cluster created by ctlptl will run
inside containers(it will serve as the virtual hosts).

Host folders which will be scaned by the nfd feature discovery should
be mounted into the container ( the virtual host). otherwise the nfd-worker
container which run inside the virtual host will just see the default base
image rootfs /boot, /lib folders, which are usually empty, leads to the
discovey failure.

Signed-off-by: Chaoyi Huang <[email protected]>

Author: ChaoyiHuang

docs/developer-guide/index.md

@@ -256,19 +256,27 @@ the steps below.
 1. Install [kustomize](https://github.com/kubernetes-sigs/kustomize)
 1. Install [tilt](https://docs.tilt.dev/install.html)
 1. Create a local Kubernetes cluster
+    - Create image registry first
+    - Create a Kubernetes cluster. Please note that docker containers will be
+      served as controller node and worker nodes, and NFD-worker will run as a
+      DaemonSet in nested container. Therefore, to make sure the NFD-worker can
+      discover the host features, the host folders "/boot" and "/lib" should be
+      mounted into worker node docker containers when creating the Kubernetes
+      cluster.
+1. Start up node feature discovery development environment
+    To start up your Tilt development environment, run at the root of your
+    local NFD codebase.
+
+    ```shell
+    tilt up
+    ```
 
-To start up your Tilt development environment, run
-
-```shell
-tilt up
-```
-
-at the root of your local NFD codebase. Tilt will start a web interface in the
-localhost and port 10350. From the web interface, you are able to see how NFD worker
-and master are progressing,  watch their build and runtime logs. Once your code changes
-are saved locally, Tilt will notice it and re-build the container image from the
-current code, push the image to the registry and re-deploy NFD pods with the latest
-container image.
+    Tilt will start a web interface in the localhost and port 10350. From the
+    web interface, you are able to see how NFD worker and master are
+    progressing, watch their build and runtime logs. Once your code changes are
+    saved locally, Tilt will notice it and re-build the container image from
+    the current code, push the image to the registry and re-deploy NFD pods
+    with the latest container image.
 
 ### Environment variables