*: Update changelogs ahead of release

Author: Jannis

packages/indexer-agent/CHANGELOG.md

@@ -5,6 +5,8 @@ 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]
+
+## [0.9.0-alpha.4] - 2020-12-20
 ### Fixed
 - Fix race condition between registering and pause/operator detection (#167)
 
@@ -182,7 +184,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 - Update @graphprotocol/common-ts to 0.2.2
 
-[Unreleased]: https://github.com/graphprotocol/indexer/compare/v0.9.0-alpha.3...HEAD
+[Unreleased]: https://github.com/graphprotocol/indexer/compare/v0.9.0-alpha.4...HEAD
+[0.9.0-alpha.4]: https://github.com/graphprotocol/indexer/compare/v0.9.0-alpha.3...v0.9.0-alpha.4
 [0.9.0-alpha.3]: https://github.com/graphprotocol/indexer/compare/v0.4.5...v0.9.0-alpha.3
 [0.4.5]: https://github.com/graphprotocol/indexer/compare/v0.4.4...v0.4.5
 [0.4.4]: https://github.com/graphprotocol/indexer/compare/v0.4.3...v0.4.4