fix: Expose main/renderer for deep import

[HazAT]

This indirectly fixes
#142
#92

since this PR removes this https://github.com/getsentry/sentry-electron/compare/fix/bump-mod-require?expand=1#diff-d99e72de0bd44751f9da4e3935d68f84R245

Now if you run into the mod.require issue you can import the SDK differntly:

import { init } from '@sentry/electron/dist/main'
import * as Sentry from '@sentry/electron'

[dperetti]

With this way of importing init, webpack will complain that "Critical dependency: the request of a dependency is an expression"

WARNING in ./node_modules/encoding/lib/iconv-loader.js 9:12-34
Critical dependency: the request of a dependency is an expression
 @ ./node_modules/encoding/lib/encoding.js
 @ ./node_modules/electron-fetch/lib/index.es.js
 @ ./node_modules/@sentry/electron/dist/main/uploader.js
 @ ./node_modules/@sentry/electron/dist/main/backend.js
 @ ./node_modules/@sentry/electron/dist/main/index.js
 @ ./src/browser/js/browser.js
 @ multi ./src/browser/js/browser.js```