Update CHANGELOG

Author: mmistakes

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Added
 - Accessibility enhancements for Lunr search form.
+- Add SCSS `$intro-image-color-overlay` variable to disable color overlay on hero images. [#55](https://github.com/mmistakes/jekyll-theme-basically-basic/issues/55)
 
 ### Fixed
 - Fix Firefox [flexbox bug](https://bugzilla.mozilla.org/show_bug.cgi?id=939897) when printing pages.