[TNZ-124370] Add kong-operator marketing README

[javsalgar]

Summary

• Add the Docker Hub marketing README for the new kong-operator container image (bitnami/kong-operator/README.md), mirroring the structure recently used for reloader (short "What is X?" blurb, upstream link, Bitnami Secure Images blurb).
• kong-operator is a Kubernetes Operator (https://github.com/kong/kong-operator, Apache-2.0) that manages Kong Gateway control/data planes declaratively via CRDs. The image itself is a FROM scratch, non-root (UID 1001), FIPS-enabled build of the static manager Go binary.
• Part of the broader TNZ-124370 kong-operator onboarding sequence; depends on the container/EAM PRs already merged in tac-app-catalogue and containers-private.

Caveat

• No published image tag / icon assets exist yet in this repo for kong-operator (those land via a separate htdocs/asset PR in this same sequence), so this README is best-effort content that can be refined once those land.

Test plan

• Verified structure matches bitnami/reloader/README.md and other recently onboarded operator-style products (e.g. agentgateway, authentik).

ai-assisted=yes