Document how to export the obsreport data

[rakyll]

As of today, obsreport can collect and report telemetry data from the collector itself but it's not documented how to export the data. Adding a README to this package directory would be sufficient to increase the visibility of obsreport and document how to export data.

[bogdandrutu]

@rakyll we intentionally postpone that until otel-go is ready. We want to change obsreport to use otel also the config story should be otel based not opencensus.

[matthewgrossman]

Any update on this? We're trying to debug some latency spikes in our collector and feel like we don't know how to best approach it. A bunch of source code spelunking shows mentions to obsreport, but not much in the docs about how to actually use this data. Thanks!

[iblancasa]

Are these the metrics exposed in the telemetry section or others? https://opentelemetry.io/docs/collector/internal-telemetry/#activate-internal-telemetry-in-the-collector