fix(overmind): properly export statecharts

Author: christianalfoni

packages/node_modules/overmind/src/config/index.ts

@@ -1,4 +1,4 @@
 export { merge } from './merge'
 export { namespaced } from './namespaced'
 export { lazy } from './lazy'
-export { statechart, Statechart } from './statechart'
+export { statecharts, Statechart } from './statecharts'

packages/node_modules/overmind/src/index.ts

@@ -13,7 +13,6 @@ import {
   VALUE,
 } from 'proxy-state-tree'
 
-import { Derived } from './derived'
 import { Devtools, DevtoolsMessage, safeValue, safeValues } from './Devtools'
 import {
   DefaultMode,