chore(deps): update quay.io/skopeo/stable docker tag to v1.18.0

The replaced module gopkg.in/yaml.v3 enforce an indentation of 4 spaces, when 0
spaces are defined. This is sad, because the old behavior can not be reproduced.

Instead of using 4 spaces for indentation, when `yamlEncoder.SetIndent(0)` is
called, we call `yamlEncoder.SetIndent(2)` to use 2 spaces for indentation,
because it is closer to 0 instead 4 spaces.

.drone.yml

@@ -456,7 +456,7 @@ steps:
       from_secret: container_image_registry_user
     DEST_CRED_PASSWORD:
       from_secret: container_image_registry_password
-  image: quay.io/skopeo/stable:v1.17.0
+  image: quay.io/skopeo/stable:v1.18.0
 
 - name: email-notification
   environment:
@@ -696,7 +696,7 @@ steps:
       from_secret: container_image_registry_user
     DEST_CRED_PASSWORD:
       from_secret: container_image_registry_password
-  image: quay.io/skopeo/stable:v1.17.0
+  image: quay.io/skopeo/stable:v1.18.0
 
 - name: email-notification
   environment:

cmd/root.go

@@ -100,12 +100,12 @@ func run(cmd *cobra.Command, args []string) error {
 		defer f.Close()
 
 		yamlEncoder := yaml.NewEncoder(f)
-		yamlEncoder.SetIndent(0)
+		yamlEncoder.SetIndent(2)
 		return yamlEncoder.Encode(dockerComposeConfig)
 
 	default:
 		yamlEncoder := yaml.NewEncoder(os.Stdout)
-		yamlEncoder.SetIndent(0)
+		yamlEncoder.SetIndent(2)
 		return yamlEncoder.Encode(dockerComposeConfig)
 	}