Update docs for Rollout specification.md

Add blueGreen activeMetadata / previewMetadata as its part of the spec.

Signed-off-by: Andre Marcelo-Tanner <andre@ada.support>

docs/features/specification.md

@@ -88,7 +88,6 @@ spec:
 
     # Blue-green update strategy
     blueGreen:
-
       # Reference to service that the rollout modifies as the active service.
       # Required.
       activeService: active-service
@@ -151,6 +150,18 @@ spec:
         requiredDuringSchedulingIgnoredDuringExecution: {}
         preferredDuringSchedulingIgnoredDuringExecution:
           weight: 1 # Between 1 - 100
+
+      # activeMetadata will be merged and updated in-place into the ReplicaSet's spec.template.metadata
+      # of the active pods. +optional
+      activeMetadata:
+        labels:
+          role: active
+
+      # Metadata which will be attached to the preview pods only during their preview phase.
+      # +optional
+      previewMetadata:
+        labels:
+          role: preview
 
     # Canary update strategy
     canary: