Add instrumentation details to each README.md

[breedx-splk]

New users have no quick/easy way to determine what telemetry is provided by the various instrumentations here. This is a tracking issue and proposal to add specific details about the telemetry generated by each instrumentation.

For each instrumentation module, there should be a corresponding README.md file that provides:

• a description what the instrumentation does
• whether it is enabled by default via the agent
• how to configure it
• specific details about the instrumentation it provides.

Here is an instrumentation checklist that should be complete before this issue can be closed:

• Activity (Add docs for Activity instrumentation telemetry #750)
• ANR (application not responding) (Add ANR docs #787)
• Crash reporting (Crash readme #788)
• Fragment
• HttpUrlConnection
• Network (Add docs for network change #789)
• OkHttp
• Session (covered in Add new session instrumentation #719)
• SlowRendering
• Startup
• Volley

[magda-woj]

@breedx-splk I'd love to take on some of those (e.g. Fragment, Https, Slow Rendering?)

[breedx-splk]

@breedx-splk I'd love to take on some of those (e.g. Fragment, Https, Slow Rendering?)

Great! Thanks. I'll stay away from Fragment then while you take it.