Sample code which demonstrates the usage of CSS in JS with TypeStyle library in SharePoint Framework.
Blog post - Styling SharePoint Framework components using CSS in JS approach
Styling SharePoint Framework components using CSS in JS approach
https://spblog.net/post/2020/04/22/styling-sharepoint-framework-components-with-css-in-js-approach
Blog post - Styling SharePoint Framework components using CSS in JS approach
Styling SharePoint Framework components using CSS in JS approach
https://spblog.net/post/2020/04/22/styling-sharepoint-framework-components-with-css-in-js-approach