Multi-application workspace support

[eugene-falk]

At the recent webinar (41:00) was said that multi-app support for open-tools (ext-gen) was for consideration.

1. Is it still on the roadmap?
2. What is the "manual" way to upgrade such project from Ext JS 6.2 and migrate it to open-tools?

sencha app build must be run from each app directory (not a workspace root).
But npm run build (which uses webpack and sencha app build under the hood) works only in current directory.
Adding package.json, webpack.config.js, workspace.json and index.js to every app directory and trying to build each app – brings never ending uninformative errors and build fails.

CC @mgusmano