Add CSS/SASS in a Sencha CMD build

Good day,

I've got one simple question about ExtJS, using Sencha CMD. What is the correct method of adding custom CSS (or Sass) code to the project? I prefer not adding a complete new theme, since the CSS instructions won't be that much.

It's easy in Sencha Touch (using app.json), but that doesn't work in ExtJS. I've got the ExtJS in Action book and looked up the forums, I can't find an answer to this simple question.

Thanks in advance,