feat(overmind): addFlushListener

Author: christianalfoni

packages/node_modules/overmind/src/index.ts

@@ -7,6 +7,7 @@ import {
   IMutation,
   VALUE,
   IMutationCallback,
+  IFlushCallback,
 } from 'proxy-state-tree'
 import { Derived } from './derived'
 import { Devtools, Message, safeValue, safeValues } from './Devtools'
@@ -631,6 +632,9 @@ export class Overmind<Config extends Configuration> implements Configuration {
   addMutationListener = (cb: IMutationCallback) => {
     return this.proxyStateTree.onMutation(cb)
   }
+  addFlushListener = (cb: IFlushCallback) => {
+    return this.proxyStateTree.onFlush(cb)
+  }
 }
 
 /*