message: Add onError doc
diff: @@ -291,6 +291,26 @@ export class MyProvider implements OnResponse {
  [API of `OnResponse` is available here](/docs/api/core/api-interfaces-onresponse)
  [API of `ModuleSessionInfo` is available here](/docs/api/core/api-classes-modulesessioninfo)
  +### `OnError` hook (experimental)
  +
  +It takes one parameter that contains `Error`, and this method gets called if any error thrown inside resolvers.
  +
  +```typescript
  +import { Injectable } from '@graphql-modules/di';
  +import { OnError } from '@graphql-modules/core';
  +
  +@Injectable()
  +export class MyProvider implements OnError {
  +
  + onResponse(error: Error) {
  + // ...do your magic...
  + logError(error.message);
  + }
  +}
  +```
  +
  +> Note that; this hook is not called if there is a DI or context build error, because DI stops working if there is some of those.
  +
  ### `OnConnect hook`
  This hook is similar to `OnRequest` hook, but this is called on the initialization of WebSockets connection. It is exactly same with `OnConnect` hook that is passed to `subscriptions` in **[SubscriptionServer](https://github.com/apollographql/subscriptions-transport-ws)**.
  