Add changelog

CHANGELOG.md

@@ -0,0 +1,18 @@
+# Changelog
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
+
+## 0.1.0 - 2021-12-20
+
+### Added
+- Initial implementation, including...
+- Parsing
+    - `INCLUDE`, `TIMEZONE`, `NOTE` and `TASK` commands
+    - `DATE`, `BDATE`, `FROM`, `UNTIL`, `MOVE` and `EXCEPT` statements
+- CLI
+    - `--file`, `--date` and `--range` arguments
+    - `show`, `done` and `fmt` commands
+- Readme
+- This changelog
+- Example file
+- Git pre-commit hook ensuring code is formatted