Prepare release 1.16

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

Signed-off-by: Ed Morley <501702+edmorley@users.noreply.github.com>

Author: edmorley

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [unreleased] - YYYY-MM-DD
+
+## [1.16] - 2026-02-26
 ### Changes
 - Changed the S3 URLs used for downloads to use AWS' dual-stack (IPv6 compatible) endpoint.