Bug Description:

Steps to Reproduce:

1. git clone repo
2. yarn
3. build error with lint error

There was no lib folder under packages/plugin-ext, and when i tried to build plugin-ext manually, I got problems of lint.

Additional Information

• Operating System: macos 12.2.1
• Theia Version: @theia/core@1.26.0 @theia/plugin-ext@1.26.0