Add missing changelog from previous PRs

Author: benoit74

CHANGELOG.md

@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Set a user-agent for `handle_user_provided_file` #103
+
+### Changed
+
+- Migrate to generic syntax in all std collections #140
+
 ### Fixed
 
 - Do not modify the ffmpeg_args in reencode function #144