docs(argo-rollouts): add more description for secret creation

Signed-off-by: st-myk <93274808+st-myk@users.noreply.github.com>

charts/argo-rollouts/values.yaml

@@ -456,7 +456,8 @@ notifications:
     create: true
 
   secret:
-    # -- Whether to create notifications secret
+    # -- Whether to create notifications secret. 
+    ## If you want to manually create secret, do not forget to add proper label to it: "app.kubernetes.io/component: rollouts-controller".
     create: false
     # -- Generic key:value pairs to be inserted into the notifications secret
     items: {}