Add CHANGELOG

CHANGELOG.md

+# Changelog
+
+## [Unreleased]
+
+## 0.2.0 - 2020-07-21
+
+### Added
+
+- Added a `do_parse/4` clause to skip mentions when we're already skipping something else (eg, when inside a link)
+
+### Fixed
+
+- Fixed a typo in the readme
+
+### Changed
+
+- Refactored `Linkify.Parser.parse/2` to enumerate over the types instead of the opts
+- Update dependencies
+
+## 0.1.0 - 2019-07-11
+
+- Initial release