chore(docs): Add mentioning of HOSTNAME env variable for standalone output (#52804)
### What?
Update documentation to mention a `HOSTNAME` env variable for `standalone` output
Related to Feature: https://github.com/vercel/next.js/pull/44627
### Why?
Current documentation mentions only `PORT` env, but does not mention `HOSTNAME` added in January
Affected documentation pages:
- https://nextjs.org/docs/app/api-reference/next-config-js/output
Affected examples:
- https://github.com/vercel/next.js/tree/canary/examples/with-docker
- https://github.com/vercel/next.js/tree/canary/examples/with-docker-multi-env
### How?
- Run examples
- Check documentation