This plugin accepts the following configuration options:
-`theme`: a separate id of one of the [themes bundled with Shikiji](https://shikiji.netlify.app/themes). One for light mode and one for dark mode. Defaults to `theme: {light: "github-light", dark: "github-dark" }`.
-`keepBackground`: If set to `true`, the background of the Shikiji theme will be used. With `false` (default) the Quartz theme color for background will be used instead.
In addition, you can further override the colours in the `quartz/styles/syntax.scss` file.