docs/k8s: add example about setting up a subnet router

Signed-off-by: Robert <rspier@pobox.com>
Co-authored-by: Maisem Ali <3953239+maisem@users.noreply.github.com>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f