Please add Server-Send-Events on changes to the json data

Would be nice if the json-server would offer [server-send-events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events) when data gets created, modified or deleted.
Front-ends then could use [EventSource](https://developer.mozilla.org/en-US/docs/Web/API/EventSource) to get notified and can react on the changes.
