Add analytics

[GentlemanHal]

It would be nice to know how people are using Nevergreen.

One of the principles we follow is including all dependencies so that people can self host on machines with no access to the internet (why we include fonts instead of using CDNs for example). This is something we need to keep in mind when implementing this feature.

• Any code should fail gracefully and silently if sending analytics fails
• Add a help section explaining we use analytics
• Should we allow users to turn it off?
  • Just if self hosting?
• Should we integrate directly with a provider or use something like Segment analytics.js?
• What events do we want to track, every button click?

[GentlemanHal]

Found out about Navigator.sendBeacon which might be good enough.