docs(react-form): add type=submit in form-composition.md subscribe button (#1521)

Author: MrGeniusProgrammer

docs/framework/react/guides/form-composition.md

@@ -124,7 +124,11 @@ function SubscribeButton({ label }: { label: string }) {
   const form = useFormContext()
   return (
     <form.Subscribe selector={(state) => state.isSubmitting}>
-      {(isSubmitting) => <button disabled={isSubmitting}>{label}</button>}
+      {(isSubmitting) => (
+        <button type="submit" disabled={isSubmitting}>
+          {label}
+        </button>
+      )}
     </form.Subscribe>
   )
 }