fix(overmind-angular): expose angular service on package entry

Author: christianalfoni

packages/node_modules/overmind-angular/src/index.ts

@@ -3,7 +3,7 @@ import { NgModule } from '@angular/core'
 import { OvermindTrackDirective, OVERMIND_INSTANCE } from './directive'
 import { OvermindService } from './service'
 
-export { OVERMIND_INSTANCE }
+export { OVERMIND_INSTANCE, OvermindService }
 
 @NgModule({
   declarations: [OvermindTrackDirective],