add CHANGELOG

Author: Phil Varner

CHANGELOG.md

@@ -0,0 +1,20 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Deprecated
+
+### Added
+
+### Fixed
+
+### Changed
+
+- Elasticsearch index mappings updated to be more thorough.
+
+### Removed

README.md

@@ -4,6 +4,8 @@ Elasticsearch backend for stac-fastapi.
 
 **WIP** This backend is not yet stable (notice no releases yet), so use the pgstac backend instead.
 
+For changes, see the [Changelog](CHANGELOG.md).
+
 ## Development Environment Setup
 
 Install [pre-commit](https://pre-commit.com/#install).