Document new secrets needed in secrets.yml

group_vars/all/secrets.yml.contents

@@ -1,4 +1,5 @@
 # These are the variables contained in secrets.yml
+# Secrets are usually 32 characters or more, matching [a-Z0-9]
 
 postgres_passwords:
   fider: xxx
@@ -25,3 +26,7 @@ drone_secrets:
   oauth_client_id: xxx
   oauth_client_secret: xxx
   rpc_shared_secret: xxx
+
+restic_secrets:
+  user_secret: xxx
+  encryption_secret: xxx