How to share or access custom css/styles from outside a sharepoint hosted add-in?

We have created some custom SharePoint hosted add-ins and added them on to a Page. These add-ins have some custom styles that are common however, they are not shared.

Is there a way by which I can put these custom styles in a common location (i.e. outside the add-in web) and access the same file across these different addins? I also dont want to load the shared css file to to be loaded indidvidually for each of the add-ins?

Thanks