chore(analytics): add Scarf to npm install, docs, and ui

[aviaviavi]

As discussed with @JamieSlome directly, this PR adds basic usage tracking tooling with Scarf, compliant with CNCF guidelines.

There are a few code-level modifications in this PR:

• Basic metrics for npm installs
• Adding a Scarf pixel to the documentation
• Adding a Scarf pixel to the footer of the UI, for basic metrics of when the UI is loaded for the first time.

As with all Scarf-based tracking, these metrics are fully anonymized and GDPR-compliant. No PII is being retained or exposed from this change.

I have the organization for git-proxy set up in Scarf, @JamieSlome as soon as you make an account I can transfer org ownership to you, and you'll be able to add any and all project maintainers.