Add analytics

[jenweber]

It would be useful to know which sections people look at the most in these guides.

This ticket is blocked until we have designs for a GDPR notice.

To-do:

• get notice banner designs
• create a component for the GDPR banner either here or in the template repo
• Add google analytics - maybe use https://github.com/poteto/ember-metrics? Or this might already be implemented in Guidemaker if we just provide our config. Needs research.
• Connect deployed domain in the Analytics console
• Exclude IP addresses of maintainers from metrics
• deploy and test