Run type check for all web app packages in CI (#22578)

* Fix incorrect usage of types pacakge

* Make platform packages properly expose their type definitions

* Have Boards, Channels, and Playbooks get types from platform packages properly

* Run type check for all web app packages in CI

* Fix incorrect job name

webapp/platform/client/package.json

@@ -10,7 +10,8 @@
   "files": [
     "lib"
   ],
-  "main": "./lib/index.js",
+  "main": "lib/index.js",
+  "types": "lib/index.d.ts",
   "repository": {
     "type": "git",
     "url": "github:mattermost/mattermost-webapp",