How to use a custom font in addon

Hi. I’m trying to make a simple addon that changes the font on webpages to a specific google font using mv3. I’ve tried referencing the fonts online url as well as using a data URI and get a CSP error. Now I’m trying to including the font in web_accessible_resources, but no luck. I’ve searched quite widely for an example as well… Thanks

Can you post the code you’ve written so far?