make wp-config writable before writing to it

wp-cli-docker/roles/wordpress-init/tasks/main.yml

@@ -43,6 +43,7 @@
     path: "{{ wordpress_homedir }}/wp-config.php"
     owner: "{{ wp_user }}"
     group: "{{ wp_group }}"
+    mode: 0640
   ignore_errors: true
   when: config.stat.exists