use array initializer value as the default for example

src/main/resources/fabric.mod.json

@@ -4,7 +4,9 @@
   "description": "This is an example description! Tell everyone what your mod is about!",
   "version": "1.0.0",
   "side": "universal",
-  "initializer": "net.fabricmc.example.ExampleMod",
+  "initializers": [
+    "net.fabricmc.example.ExampleMod"
+  ],
   "requires": {
     "fabric": "*"
   },