Prepare changelog for v15.2.0

Author: RiotRobot

CHANGELOG.md

@@ -1,3 +1,14 @@
+Changes in [15.2.0](https://github.com/matrix-org/matrix-js-sdk/releases/tag/v15.2.0) (2021-12-06)
+==================================================================================================
+
+## ✨ Features
+ * Remove support for `ArrayBuffer` in unstable MSC3089 `createFile()` and `createNewVersion()` and instead use same content types as handled by `MatrixClient.uploadContent()`. This enables support for Node.js. ([\#2014](https://github.com/matrix-org/matrix-js-sdk/pull/2014)).
+ * Support for password-based backup on Node.js ([\#2021](https://github.com/matrix-org/matrix-js-sdk/pull/2021)).
+ * Add optional force parameter when ensuring Olm sessions ([\#2027](https://github.com/matrix-org/matrix-js-sdk/pull/2027)).
+
+## 🐛 Bug Fixes
+ * Fix call upgrades ([\#2024](https://github.com/matrix-org/matrix-js-sdk/pull/2024)). Contributed by @SimonBrandner.
+
 Changes in [15.2.0-rc.1](https://github.com/matrix-org/matrix-js-sdk/releases/tag/v15.2.0-rc.1) (2021-11-30)
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