feat: Support Electron utility process

[timfish]

Closes #987

utility.js

import * as Sentry from '@sentry/electron/utility';

// No config required in utility process
Sentry.init();

main.js

import * as path from 'path';
import * as Sentry from '@sentry/main';
import { app, utilityProcess } from 'electron';

Sentry.init({
  dsn: '__DSN__'
});

app.on('ready', () => {
  // No special config required in the main process, just fork as before
  const child = utilityProcess.fork(path.join(__dirname, 'utility.js'));
});

How it works

We wrap electron.utilityProcess.fork which allows us to set up a message port between the processes. All events from the utility process are passed to the main process via a custom transport. This way we retain the offline support, events get the full Electron context and all events go through the main process beforeSend callback.

Unlike renderer processes, utility processes do not yet sync scope (ie. user, tags, extra, etc) to the main process.

[AbhiPrasad]

Let's make sure to update docs. Should we update https://github.com/getsentry/sentry-wizard as well?

[timfish]

Will definitely need adding to the docs. Not sure this Electron feature is widely used enough to warrant adding to the wizard 🤔