Use ACTIONS_RUNNER_CONTAINER_HOOK_TEMPLATE to extend service containers (#134)

https://github.com/actions/runner-container-hooks/issues/132

Co-authored-by: Katarzyna Radkowska <katarzyna.radkowska@sabre.com>

examples/extension.yaml

@@ -9,7 +9,7 @@ spec:
     runAsGroup: 3000
   restartPolicy: Never
   containers:
-  - name: $job # overwirtes job container
+  - name: $job # overwrites job container
     env:
     - name: ENV1
       value: "value1"
@@ -20,11 +20,22 @@ spec:
     args:
     - -c
     - sleep 50
+  - name: $redis # overwrites redis service
+    env:
+      - name: ENV2
+        value: "value2"
+    image: "busybox:1.28" # Ignored
+    resources:
+      requests:
+        memory: "1Mi"
+        cpu: "1"
+      limits:
+        memory: "1Gi"
+        cpu: "2"
   - name: side-car
     image: "ubuntu:latest" # required
     command:
-    - sh
+      - sh
     args:
-    - -c
-    - sleep 60
-    
+      - -c
+      - sleep 60