Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

webapp/platform/client/src/index.ts

@@ -0,0 +1,13 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+export {
+    default as Client4,
+    ClientError,
+    DEFAULT_LIMIT_AFTER,
+    DEFAULT_LIMIT_BEFORE,
+} from './client4';
+
+export type {TelemetryHandler} from './telemetry';
+export type {WebSocketMessage} from './websocket';
+export {default as WebSocketClient} from './websocket';