Add potx to extract translation strings

composer.json

@@ -49,6 +49,7 @@
     "drupal/core": "*",
     "drupal/core-composer-scaffold": "*",
     "drupal/devel": "*",
+    "drupal/potx": "*",
     "drupal/schema_diff": "*",
     "drupal/webprofiler": "*",
     "lakedrops/ahoy": "*",