Revert tsconfig.json change to avoid needing a manual upgrade step in projects

[Haprog]

Since #9109 the feature/offline branch uses TS in the service worker and needs to have "lib": ["webworker"] in tsconfig.json to avoid randomly failing webpack build. However we have no mechanism (at least currently) to do any updates to existing tsconfig.json in the project so we need to at least make sure to include this information in release notes as upgrade instructions, otherwise when upgrading to this version the webpack build will start failing randomly if you don't make this update to tsconfig.

[vlukashov]

Adding "lib": ["webworker"] to the root tsconfig.json file would silence the TS compiler in cases if the developer uses some of the Service Worker APIs in the main application code where they are not available. This is not ideal.

A different approach would be adding /// <reference lib="webworker" /> to the top of the generated sw.ts file (as suggested in microsoft/TypeScript#11781), or moving the sw.ts file into a separate folder with its own tsconfig.json (as suggested in https://stackoverflow.com/questions/56356655/structuring-a-typescript-project-with-workers).

[Haprog]

@vlukashov That sounds like a better solution. Thanks for the insights! I guess we can still use this issue to fix it (revert changes to tsconfig and add the lib reference comment to sw.ts if that makes it work).