Add telemetry tracking to CLI tool

[michielmulders]

Description: I would like to track telemetry data for the CLI tool, like command usage, to better understand how users use the CLI. Regular metrics like GitHub stars or NPM downloads are skewed by nature because a single person can account for 90% of the usage in some cases.

Notes:

• Make it opt-in instead of opt-out for GDPR/privacy concerns (global env flag to opt-out -> e.g. within a CI pipeline -> but how do you segment whether the usage is coming from a person (UI) or a CI pipeline).

It's usually typical across providers to inject a "CI" env variable, so I would check for that. In Node that's just process.env.CI -- this can also sometimes be detected through other env variables.

Aha, as I thought, there's a package for this: https://www.npmjs.com/package/is-ci
That is assuming your CLI is usable in CI, sometimes it's not.

• Figure out what to track and how we will use the data (be purposeful) -> e.g. metrics per command to understand which commands are used more than others

References:

• Next.js CLI telemetry
• Are there any open source tools to build the telemetry server?