Migrate relevant docs to opentelemetry.io

[chalin]

The docs folder seems to have rich content. Would it make sense to publish some of the pages on opentelemetry.io?

(This initiative is in support of open-telemetry/opentelemetry.io#833.)

/cc @austinlparker

[mateuszrzeszutek]

Related issue: #1580

[trask]

@chalin do you have thoughts on which additional docs make sense to (eventually) move to the web site?

[mateuszrzeszutek]

I mentioned it here: #6408 (comment), but let me call it out explicitly in this thread:
I like the notion of moving all the user-facing docs, such as instrumentation libraries' READMEs, to the opentelemetry.io website. I think it's much better suited to be THE first place (and, hopefully, for most people the only place) to go to when you want to learn how to use SDK/javaagent/a particular instrumentation than READMEs in this GH repo.

[jaydeluca]

at this point I believe we now have the general usage information on the documentation site. Do we still think it would be good to move all the individual instrumentation readmes?

[trask]

let's go ahead and close, keeping individual instrumentation readmes in this repo, we can always revisit that decision later