Add CHANGELOG

Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

CHANGELOG.md

@@ -16,6 +16,11 @@ We use *breaking* word for marking changes that are not backward compatible (rel
 - [#2238](https://github.com/thanos-io/thanos/pull/2238) Ruler: Fixed Issue #2204 bug in alert queue signalling filled up queue and alerts were dropped
 - [#2231](https://github.com/thanos-io/thanos/pull/2231) Bucket Web - Sort chunks by thanos.downsample.resolution for better grouping
 
+### Added
+
+- [#2250](https://github.com/thanos-io/thanos/pull/2250) Compactor: Enable vertical compaction for offline deduplication (Experimental). Uses `--deduplication.replica-label` flag to specify the replica label to deduplicate on (Hidden). Also, adds `--run-interval` to specify compaction run interval when compact runs with `--wait` enabled.
+
+
 ## [v0.11.0](https://github.com/thanos-io/thanos/releases/tag/v0.11.0) - 2020.03.02
 
 ### Fixed