Add CHANGELOG entry

Signed-off-by: Filip Petkovski <filip.petkovsky@gmail.com>

CHANGELOG.md

@@ -14,6 +14,8 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 
 - [#5990](https://github.com/thanos-io/thanos/pull/5990) Cache/Redis: add support for Redis Sentinel via new option `master_name`.
 - [#6008](https://github.com/thanos-io/thanos/pull/6008) *: Add counter metric `gate_queries_total` to gate.
+- [#6074](https://github.com/thanos-io/thanos/pull/6074) *: Add histogram metrics `thanos_store_server_series_requested` and `thanos_store_server_chunks_requested` to all Stores.
+- [#6074](https://github.com/thanos-io/thanos/pull/6074) *: Allow configuring series and chunk rate limits per `Series` request for all Stores.
 
 ### Changed