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/boards/src/plugin_entry.ts

@@ -0,0 +1,14 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+import manifest from './manifest'
+
+import Plugin from './index'
+
+declare global {
+    interface Window {
+        registerPlugin(id: string, plugin: Plugin): void
+    }
+}
+
+window.registerPlugin(manifest.id, new Plugin())