Add Service Worker Support

[albert-gonzalez]

Hi!

Is your feature request related to a problem? Please describe.
We have a Chrome extension that sends events using your lib in the foreground (called content script) and in the background (a service worker). In the foreground, we can use your browser tracker without problems, but we can't use this in the service worker due to these issues:

• Browser Tracker needs a window object to work, and service workers don't have it.
• Browser Tracker uses XHR to send events, and service workers use fetch only.

We developed a workaround to send events in the background using the Core Tracker and a port of the Node Emitter, but using fetch instead of got.

Describe the solution you'd like
It would be nice if your library supported service workers.

Thank you for your time!

[kamil-cf]

Any updates on this issue? We could use node-tracker for now just to make it works, but it doesn't send a lot of useful properties that JS tracker used to send.