switch to css modules

Should ocmpartmentlaize css -- this looksl ike it wil lb epretty easy to do, cf https://www.gatsbyjs.org/tutorial/part-two/#using-component-scoped-css

https://www.robinwieruch.de/react-css-modules

cf also this guide to styled components:

https://www.robinwieruch.de/react-styled-components