add documentation about local image build (#129)

Signed-off-by: Felix Breuer <f.breuer94@gmail.com>

Author: breuerfelix

docs/development.md

@@ -1,8 +1,10 @@
-# Local Development Guide
+# Development
+
+## Run MCM locally
 
 This guide describes how to run the STACKIT MCM provider against a real Gardener shoot on STACKIT. A local kind cluster is not suitable because the provider creates real STACKIT VMs that must join a real Kubernetes cluster.
 
-## Prerequisites
+### Prerequisites
 
 Before you begin, ensure you have the following:
 
@@ -11,7 +13,7 @@ Before you begin, ensure you have the following:
 - Access to the seed and shoot via `gardenctl`
 - A local Go toolchain
 
-## Overview
+### Overview
 
 You will run the provider and MCM locally while pointing them at real clusters:
 
@@ -21,7 +23,7 @@ You will run the provider and MCM locally while pointing them at real clusters:
 
 MachineClass objects and Secrets are assumed to already exist. Running the provider locally results in faster feedback loops when developing new features and enables using the go debugger.
 
-## 1. Get kubeconfigs with gardenctl
+### 1. Get kubeconfigs with gardenctl
 
 Set these shell variables (replace with your values):
 
@@ -48,7 +50,7 @@ export CONTROL_KUBECONFIG=/tmp/control.kubeconfig
 export CONTROL_NAMESPACE=shoot--testing--$SHOOT_NAME
 ```
 
-## 2. Scale down the in-cluster MCM
+### 2. Scale down the in-cluster MCM
 
 Scale the existing MCM in the seed to `0`, so your local controller can take over:
 
@@ -65,15 +67,15 @@ watch -n 5 "kubectl --kubeconfig '$CONTROL_KUBECONFIG' -n '$CONTROL_NAMESPACE' s
 This will check and scale down the deployment every 5 seconds.  
 Make sure to set the environment variables.
 
-## 3. Run the provider (driver)
+### 3. Run the provider (driver)
 
 Set the environment varialbes from above and run another terminal in your provider repo:
 
 ```bash
 make start
 ```
 
-## 4. Run MCM locally
+### 4. Run MCM locally
 
 On another terminal in the Gardener MCM repository:
 
@@ -88,8 +90,27 @@ Set the environment varialbes from above and run the MCM:
 make start
 ```
 
-## Notes
+### Notes
 
 - This workflow assumes MachineClass and Secret objects already exist and are valid.
 - The local controllers should reconcile existing resources and provision STACKIT VMs that join the shoot.
 - Re-enable the in-cluster MCM after testing by scaling it back up.
+
+## Build Container Image locally
+
+Create a classic personal access token in GitHub. Set an expiration date and enable the `write:packages` scope.  
+**Note:** Using a token generated by the `gh` cli is not sufficient.
+
+Login to the `ghcr.io` registry. When asked for a password, paste the access token:
+
+```bash
+ko login -u <your_username> --password-stdin ghcr.io
+```
+
+Build image and push to the regsitry:
+
+```bash
+make image
+```
+
+The pushed image name and tag are logged to the console.