Add E2E test app for basic `@sentry/browser`

[mydea]

We do not have any E2E test app that tests the base/default browser experience, including the default browserTracingIntegration etc. We should add that!

[andreiborza]

Seems like a decent candidate for the Good First Issue label.

[mahdikhashan]

is it still an open issue?

[Lms24]

Hi, no, we should close this issue as an e2e test app was added in #13125. We have some other issues though if you're interested in helping out :)