The comme style file deckdeckgo-slides.scss isn't automatically exported in the bundle as it is not related to a component. Of course it is imported and packages in the css files where it is imported but the scss itself is not part of the bundle which leads to compilation problem if the library is used in another Stencil project

In the meantime, rename the file from deckdeckgo-slides.scss to deckdeckgo-slide.scss (singular)