update changelog

Author: beanieboi

changelog.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 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).
 
+## [1.3] - 2019-08-09
+ ### Added
+ - add support for custom mime.types file https://github.com/heroku/heroku-buildpack-nginx/pull/37
+
 ## [1.2] - 2019-05-29
  ### Added
  - [heroku-18] update nginx to 1.17.0