Update composer.json (allow-plugins section) (#514)

Author: arogachev

composer.json

@@ -66,7 +66,8 @@
     "config": {
         "allow-plugins": {
             "yiisoft/yii2-composer": true,
-            "cweagans/composer-patches": true
+            "cweagans/composer-patches": true,
+            "php-http/discovery": true
         }
     },
     "extra": {