Add CHANGELOG

Signed-off-by: jojohappy <sarahdj0917@gmail.com>

CHANGELOG.md

@@ -19,6 +19,21 @@ We use *breaking* word for marking changes that are not backward compatible (rel
 
 - [#1070](https://github.com/improbable-eng/thanos/pull/1070) Downsampling works back again. Deferred closer errors are now properly captured.
 
+### Changed
+
+- [#1066](https://github.com/improbable-eng/thanos/pull/1066) Upgrade Thanos ui to Prometheus v2.9.1.
+
+ Changes from the upstream:
+ * query:
+ - [ENHANCEMENT] Update moment.js and moment-timezone.js [PR #4679](https://github.com/prometheus/prometheus/pull/4679)
+ - [ENHANCEMENT] Support to query elements by a specific time [PR #4764](https://github.com/prometheus/prometheus/pull/4764)
+ - [ENHANCEMENT] Update to Bootstrap 4.1.3 [PR #5192](https://github.com/prometheus/prometheus/pull/5192)
+ - [BUGFIX] Limit number of merics in prometheus UI [PR #5139](https://github.com/prometheus/prometheus/pull/5139)
+ - [BUGFIX] Web interface Quality of Life improvements [PR #5201](https://github.com/prometheus/prometheus/pull/5201)
+ * rule:
+ - [ENHANCEMENT] Improve rule views by wrapping lines [PR #4702](https://github.com/prometheus/prometheus/pull/4702)
+ - [ENHANCEMENT] Show rule evaluation errors on rules page [PR #4457](https://github.com/prometheus/prometheus/pull/4457)
+
 ## [v0.4.0-rc.0](https://github.com/improbable-eng/thanos/releases/tag/v0.4.0-rc.0) - 2019.04.18
 
 :warning: **IMPORTANT** :warning: This is the last release that supports gossip. From Thanos v0.5.0, gossip will be completely removed.