docs(config): link to shared declarative config spec conformance matrix (#5347)

* add declarative config spec conformance matrix

* rename changelog fragment to PR #5347

* remove stray 5346 fragment (already renamed to 5347)

* link to shared language support matrix instead of duplicating per-SDK

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Co-authored-by: Lukas Hering <40302054+herin049@users.noreply.github.com>