gatsby-theme-ui-layout
Gatsby theme for adding shadowable layouts to multiple Gatsby themes for composition.
npm i gatsby-theme-ui-layout
In your theme, import and use the Layout component, which does not include any default layout.
import { jsx } from 'theme-ui'
import { Layout } from 'gatsby-theme-ui-layout'
export default props =>
<Layout {...props}>
{/* your theme content goes here */}
</Layout>
End-users of a theme that is built with gatsby-theme-ui-layout
can shadow the same Layout component to customize the page layout.