This is a demo of an Ext JS universal application.
This app was created using Ext JS 6.5.2.463 and if you have this version of the SDK you can run the following command to repopulate this workspace with that version of the SDK.
sencha workspace install /path/to/sdks
Alternatively, you can do the following to add any version of the framework to the 'ext' folder.
sencha framework add /path/to/specific/extjs/version ext