allow override of default limit (<200) on articles on shared suppliers (#609)

lib/foodsoft_config.rb

@@ -256,6 +256,7 @@ class FoodsoftConfig
         contact: {}, # avoid errors when undefined
         tasks_period_days: 7,
         tasks_upfront_days: 49,
+        shared_supplier_article_sync_limit: 200,
         # The following keys cannot, by default, be set by foodcoops themselves.
         protected: {
           multi_coop_install: true,