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/channels/build/notice-file/config.yaml

@@ -0,0 +1,16 @@
+---
+
+title: "Mattermost Web App"
+copyright: "© 2017-present Mattermost, Inc.  All Rights Reserved.  See LICENSE.txt for license information."
+description: "This document includes a list of open source components used in Mattermost Web App, including those that have been modified."
+reviewers: 
+  - "mattermost/release-managers"
+  - "mattermost/web-platform"
+search:
+  - "package.json"
+  - "packages/**/package.json"
+dependencies: []
+devDependencies: 
+  - "webpack"
+
+...