composer.json: Add 3.0.x-dev alias for pico-3.0 branch

composer.json

@@ -51,7 +51,8 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "2.0.x-dev"
+            "dev-master": "2.0.x-dev",
+            "dev-pico-3.0": "3.0.x-dev"
         }
     }
 }