Update changelog

CHANGELOG.md

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+x.x.x Release notes (yyyy-MM-dd)
+=============================================================
+### Enhancements
+* Improve performance when using Chrome Debugging with React Native by adding caching and reducing the number of RPC calls required. Read-heavy workflows are as much as 10x faster. Write-heavy workflows will see a much smaller improvement, but also had a smaller performance hit to begin with. (PR: ([#2373](https://github.com/realm/realm-js/pull/2373))).
+
+### Fixed
+* <How to hit and notice issue? what was the impact?> ([#????](https://github.com/realm/realm-js/issues/????), since v?.?.?)
+* Opening a query-based Realm using `new Realm` did not automatically add the required types to the schema when running in Chrome, resulting in errors when trying to manage subscriptions. (PR: ([#2373](https://github.com/realm/realm-js/pull/2373))).
+* The Chrome debugger did not properly enforce read isolation, meaning that reading a property twice in a row could produce different values if another thread performed a write in between the reads. This was typically only relevant to synchronized Realms due to the lack of multithreading support in the supported Javascript environments. (PR: ([#2373](https://github.com/realm/realm-js/pull/2373))).
+* The RPC server for Chrome debugging would sometimes deadlock if a notification fired at the same time as a Realm function which takes a callback was called. (PR: ([#2373](https://github.com/realm/realm-js/pull/2373))).
+
+### Compatibility
+* Realm Object Server: 3.11.0 or later.
+* APIs are backwards compatible with all previous release of realm in the 2.x.y series.
+* File format: Generates Realms with format v9 (Reads and upgrades all previous formats)
+
+### Internal
+* None.
+
 2.27.0 Release notes (2019-5-15)
 =============================================================
 NOTE: The minimum version of Realm Object Server has been increased to 3.21.0 and attempting to connect to older versions will produce protocol mismatch errors. Realm Cloud has already been upgraded to this version, and users using that do not need to worry about this.