typedoc generation script does not work anymore

[jfaltermeier]

Bug Description:

$ npm run docs

> @theia/monorepo@0.0.0 docs
> rimraf gh-pages/docs/next && typedoc --tsconfig tsconfig.json --options configs/typedoc.json .

[error] Unknown option 'external-modulemap' You may have meant:
        name
        exclude
        externalPattern
        theme
        cname
        readme
        help
[error] The tsconfig file ./tsconfig.json does not exist
[error] Found 2 errors and 0 warnings

Probably related to yarn -> npm migration

Additional Information

• Operating System:
• Theia Version: