Update changelogs from fern repo (#4419)

Co-authored-by: Swimburger <3382717+Swimburger@users.noreply.github.com>

Author: fern-support

fern/products/sdks/overview/csharp/changelog/2026-03-20.mdx

@@ -1,3 +1,12 @@
+## 2.42.0
+**`(feat):`** Add support for HTTP/2 WebSockets via `SocketsHttpHandler`. A new `HttpInvoker`
+property on the WebSocket Options class allows passing an `HttpMessageInvoker` to
+enable multiplexing multiple WebSocket streams over a single TCP connection. When
+set, the connection factory configures `HttpVersion.Version20` and uses the
+`ConnectAsync(Uri, HttpMessageInvoker, CancellationToken)` overload on .NET 7+.
+On older targets the invoker is ignored and the standard connect path is used.
+
+
 ## 2.41.0
 **`(feat):`** Add `ConnectTimeout` property to `WebSocketConnection` and `WebSocketClient` with a
 default of 5 seconds. The connection factory call in `StartClient` now uses a linked