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/package.json

@@ -0,0 +1,29 @@
+{
+  "name": "@mattermost/webapp",
+  "private": true,
+  "scripts": {
+    "postinstall": "node scripts/skip_integrity_check.js && npm run build --workspace=platform/types --workspace=platform/client --workspace=platform/components",
+    "build": "node scripts/build.js",
+    "run": "node scripts/run.js",
+    "dev-server": "node scripts/dev-server.js",
+    "test": "npm run test --workspaces --if-present",
+    "check": "npm run check --workspaces --if-present",
+    "fix": "npm run fix --workspaces --if-present",
+    "check-types": "npm run check-types --workspaces --if-present",
+    "clean": "npm run clean --workspaces --if-present"
+  },
+  "devDependencies": {
+    "blessed": "0.1.81",
+    "chalk": "4.1.2",
+    "concurrently": "7.6.0",
+    "strip-ansi": "6.0.1"
+  },
+  "workspaces": [
+    "channels",
+    "platform/client",
+    "platform/components",
+    "platform/types",
+    "playbooks",
+    "boards"
+  ]
+}