Minify css for demo docs

rollup.config.js

@@ -6,7 +6,7 @@ import json from '@rollup/plugin-json'
 import livereload from 'rollup-plugin-livereload'
 import { terser } from 'rollup-plugin-terser'
 import babel from 'rollup-plugin-babel'
-import css from 'rollup-plugin-css-only'
+import css from 'rollup-plugin-import-css'
 import { mdsvex } from 'mdsvex'
 
 const production = !process.env.ROLLUP_WATCH
@@ -76,7 +76,7 @@ export default {
     }),
     // we'll extract any component CSS out into
     // a separate file - better for performance
-    css({ output: 'index.css' }),
+    css({ output: 'index.css', minify: true }),
 
     // If you have external dependencies installed from
     // npm, you'll most likely need these plugins. In