docs: add site-router to the reference and component lists #708

cozystack/cozystack#3426 adds new catalog app site-router (kind SiteRouter, routed site-to-site IPsec gateway running as KubeVirt VM) and new platform component site-router-controller. Both come from naas bundle and only when iaas bundle is enabled too, because gateway runs as KubeVirt VM. Nothing picks them up here automatically, so once that PR merges three places need it:

• Makefile: site-router in NETWORKING next to vpn and tcp-balancer, otherwise generator never builds reference page from its README.md
• content/en/docs/next/guides/platform-stack/_index.md: gateway image is barerouter (built from VyOS rolling sources), it needs oss-card like Outline has for vpn
• content/en/docs/next/operations/configuration/licenses.md: same card for licenses list