Migrating other 2 files from javascript to typescript (#29435)

* feat: Add initial store configuration for webapp channels

* refactor: Convert store/index.js to TypeScript with type definitions

* test: Add initial test file for store index

* refactor: Convert index.test.js to TypeScript with type annotations

* Removing old files

* Applying linter fixes

* Fixing some of the types errors

* fix: Type mock implementation of getState in global_actions.test.ts

* test: Add missing GlobalState import in global_actions.test.ts

* fix: Resolve TypeScript mock implementation error in global_actions.test.ts

* Some fixes

* Address CI problems

* Installing zen-observable types

* Addressing PR review comment

* Addressing PR review comment

* Addressing PR review comment

* Addressing PR review comment

* Addressing PR review comment

* Simpliying things

* Fixing CI

* Fixing types

webapp/channels/package.json

@@ -140,6 +140,7 @@
     "@types/shallow-equals": "1.0.3",
     "@types/styled-components": "5.1.32",
     "@types/tinycolor2": "1.4.6",
+    "@types/zen-observable": "0.8.7",
     "copy-webpack-plugin": "11.0.0",
     "emoji-datasource": "6.1.1",
     "emoji-datasource-apple": "6.1.1",