Add e2e test for browser integration on Bitbucket
Created by: felixfbecker
Ref #5294
Tests only the browser extension, not the native integration, but lays the foundation for other browser extension tests.
The browser extension has to be build with <all_urls>
permissions because puppeteer cannot accept permission prompts.
This script would be run manually before release for now, but could run against our dogfood instance.