Add Telemetry

[probably-not]

Adding telemetry to FunWithFlags would be a huge help in determining things like how often flags are being fetched from the underlying data store vs from the cache, what keys are being looked at most often, and much more.

Using the beam telemetry library has become fairly standardized as a way to report details from within libraries, allowing users a standard way of collecting metrics and details, along with doing things like allowing the collection of traces and spans from within libraries by building "spannable events".