Add instruction to test with image-builder

docs/image-builder/README.md

@@ -0,0 +1,42 @@
+# Use case: Testing packer-plugin-powervs with [image builder](https://github.com/kubernetes-sigs/image-builder)
+
+Note: The following steps are being executed on x86 VM.
+
+1. Clone packer-plugin-powervs
+   ```shell
+    $ git clone https://github.com/ppc64le-cloud/packer-plugin-powervs.git
+   ```
+2. Build the binary
+    ```
+   $ cd packer-plugin-powervs
+   $ make build
+
+   This will build binary named `packer-plugin-powervs` under current directoy.
+   ```
+3. Clone the image-builder
+    ```
+   $ git clone https://github.com/kubernetes-sigs/image-builder.git
+   ```
+4. Install the necessary dependencies for image-builder
+    ```
+   $ cd images/capi
+   $ make deps-powervs
+   ```
+   If the above command returns packages required error manually install them and retry.
+
+
+
+5. Replace the downloaded PowerVS packer plugin with binary built in step 2
+
+   1. When we run ```make deps-powervs```, It will [download and install](https://github.com/kubernetes-sigs/image-builder/blob/main/images/capi/hack/ensure-powervs.sh#L42-L52) the PowerVS plugin in `"${HOME}/.packer.d/plugins/packer-plugin-powervs"` directory.
+   2. Get the name of the downloaded binary and replace it with binary built in step 2.
+   ```shell
+   $ ls ${HOME}/.packer.d/plugins/packer-plugin-powervs/
+   $ mv /root/packer-plugin-powervs/packer-plugin-powervs ${HOME}/.packer.d/plugins/packer-plugin-powervs/packer-plugin-powervs_v0.2.1_x5.0_linux_amd64
+   ```
+
+6. Update the image-builder script to avoid downloading the packer-plugin-powervs binary again from upstream.
+   1. When we run step 7, packer-plugin-powervs binary will be downloaded again from upstream, which will replace the binary we added in step 5.
+   2. To avoid replacing of binary,edit the [ensure-powervs.sh](https://github.com/kubernetes-sigs/image-builder/blob/main/images/capi/hack/ensure-powervs.sh#L42-L52) file to remove download and moving of upstream binary.
+
+7. Run the image builder, Instructions can be found in [cluster-api-provider-ibmcloud](https://cluster-api-ibmcloud.sigs.k8s.io/developer/build-images#powervs)