Add the composer.librarie.json from the webform module.

composer.json

@@ -52,6 +52,7 @@
         "drupal/wysiwyg_linebreaks": "^1.9",
         "drush/drush": "^9.0",
         "drutopia/drutopia": "^1.0-beta1",
+        "wikimedia/composer-merge-plugin": "^1.4",
         "zaporylie/composer-drupal-optimizations": "^1.0"
     },
     "repositories": {
@@ -95,6 +96,11 @@
                 "type:drupal-drush"
             ]
         },
+        "merge-plugin": {
+            "include": [
+                "web/modules/contrib/webform/composer.libraries.json"
+            ]
+        },
         "enable-patching": true,
 	"patches": {
 	    "drupal/search404": {