fix: only containers should be readonly

src/api.ts

 import { defineStore } from 'pinia'
-import { computed, readonly, ref, Ref } from 'vue'
+import { computed, readonly, ref, Ref, shallowReadonly } from 'vue'
 import { merge } from 'lodash'
 
 type ID = number | string
@@ -127,8 +127,8 @@ export function createExtendableAPI<T extends APIObject>(
   return {
     base: {
       error: readonly(error),
-      items: readonly(items),
-      itemMap: readonly(itemMap),
+      items: shallowReadonly(items),
+      itemMap: shallowReadonly(itemMap),
       reset,
     },
     createRequest,