Enable browser tracing

[juliusknorr]

First attempt to add #329 by enabling the browser tracing plugin which automatically collects data for page navigation events https://docs.sentry.io/platforms/javascript/performance/instrumentation/automatic-instrumentation/

ToDo

• Look into backend options either through the event logger or maybe using the IProfiler bits now available in server (https://github.com/getsentry/sentry-symfony/tree/master/src seems like a good example)
• Look into connected services to link traces together https://docs.sentry.io/platforms/javascript/performance/connect-services/

[juliusknorr]

Closing as I currently have no time to finish this. Anyone is free to take over of course :)