Update CHANGELOG for 4.1.0 (#1396)

Co-authored-by: Ezra Chung <88335979+eramongodb@users.noreply.github.com>

Author: kevinAlbs

CHANGELOG.md

@@ -7,15 +7,19 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 Changes prior to 3.9.0 are documented as [release notes on GitHub](https://github.com/mongodb/mongo-cxx-driver/releases).
 
-## 4.1.0 [Unreleased]
+## 4.1.0
 
 ### Fixed
 
 - The API version of auto-downloaded C Driver libraries no longer incorrectly inherits the C++ Driver's `BUILD_VERSION` value.
+- Potentially unchecked narrowing conversion in `bsoncxx::v_noabi::builder::core::append()` now throws an exception with error code `k_cannot_append_string`.
 
 ### Added
 
 - `storage_engine()` in `mongocxx::v_noabi::options::index`.
+- Support for sort option with replaceOne and updateOne operations.
+- Support for BSON Binary Vector.
+- Support $lookup in CSFLE and QE.
 
 ### Deprecated
 
@@ -29,6 +33,10 @@ Changes prior to 3.9.0 are documented as [release notes on GitHub](https://githu
 - Bump the minimum required C Driver version to [2.0.0](https://github.com/mongodb/mongo-c-driver/releases/tag/2.0.0).
 - Set CMake maximum policy version to 4.0.
   - The CMake minimum required version is still 3.15.
+- C++17 polyfill implementations for `optional<T>` and `string_view` are now declared in the `bsoncxx::v1::stdx` namespace.
+  - The `bsoncxx::v_noabi::stdx` namespace now contains type aliases to their `v1` equivalents.
+  - This is an ABI breaking change for all symbols which reference `bsoncxx::v_noabi::stdx` in their declaration (including mongocxx library symbols).
+    - This does not affect users who compile with C++17 or newer and have not set `BSONCXX_POLY_USE_IMPLS=ON`.
 
 ## 4.0.0