move parameters to separate file

config/parameters.yaml

@@ -0,0 +1,2 @@
+parameters:
+    locale: en_US

config/services.yaml

@@ -1,4 +1,2 @@
-# Put parameters here that don't need to change on each machine where the app is deployed
-# https://symfony.com/doc/current/best_practices/configuration.html#application-related-configuration
-parameters:
-    locale: en_US
+imports:
+    - { resource: "parameters.yaml" }