Add an initial CHANGELOG.md

Based on https://keepachangelog.com/en/1.0.0

android-activity/CHANGELOG.md

@@ -0,0 +1,19 @@
+# Changelog
+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]
+### Added
+- Emit an `InputAvailable` event for new input with `NativeActivity` and `GameActivity`
+  enabling gui apps that don't render continuously
+- Oboe and Cpal audio examples added
+### Changed
+- *Breaking*: updates to `ndk 0.7` and `ndk-sys 0.4`
+
+## [0.1.1] - 2022-07-04
+### Changed
+- Documentation fixes
+
+## [0.1] - 2022-07-04
+### Added
+- Initial release