Add k8s operator injection reference into relevant SIG pages

[chalin]

Originally posted by @chalin in #1147 (comment)

I'd suggest that we merge this as is. I can then followup with a PR that distributes this comment to the Java, NodeJS and Python pages. How does that sound?

/cc @svrnm @cartermp

[svrnm]

Python has this now: https://opentelemetry.io/docs/instrumentation/python/automatic/operator/

Not sure how I feel about that page, it somehow feels redundant, otherwise it points people to the place where they should look, so we could have the same for all the other languages as well