astro/examples/with-markdown-shiki/astro.config.mjs

import { defineConfig } from 'astro/config';

// https://astro.build/config
export default defineConfig({
	// Enable Custom Markdown options, plugins, etc.
	markdown: {
		syntaxHighlight: 'shiki',
		shikiConfig: {
			theme: 'dracula',
			// Learn more about this configuration here:
			// https://docs.astro.build/en/guides/markdown-content/#syntax-highlighting
		},
	}
});