Prepare release 1.16

[edmorley]

To pick up #144.

https://github.com/heroku/heroku-buildpack-nginx#releasing-a-new-version

[edmorley]

https://github.com/heroku/heroku-buildpack-nginx/releases/tag/v1.16

$ heroku buildpacks:publish heroku-community/nginx v1.16
Publishing buildpack heroku-community/nginx... done
Publishing buildpack was successful

$ heroku buildpacks:versions heroku-community/nginx | head -n4
 Version Released At              Status
 ─────── ──────────────────────── ─────────
 18      2026-02-26T11:15:41.126Z published
 17      2025-07-21T15:59:16.649Z published