Add domain telemetry on app mount

[djhi]

In production, react-admin applications will send an anonymous request on mount to a telemetry server operated by marmelab. You can see this request by looking at the Network tab of your browser DevTools:

https://react-admin-telemetry.marmelab.com/react-admin-telemetry

The only data sent to the telemetry server is the admin domain (e.g. "example.com") - no personal data is ever sent, and no cookie is included in the response. The react-admin team uses these domains to track the usage of the framework.

You can opt out of telemetry by simply adding disableTelemetry to the <Admin> component:

// in src/App.js
import * as React from "react";
import { Admin } from 'react-admin';

const App = () => (
    <Admin disableTelemetry>
        // ...
    </Admin>
);