composer.json: develop as v4.x-dev

Author: ek9

composer.json

@@ -54,6 +54,7 @@
     "extra": {
         "branch-alias": {
             "dev-master": "3.2.x-dev",
+            "dev-develop": "4.x-dev",
             "dev-v3.1": "3.1.x-dev"
         }
     }