Optimise amount of initial CSS

lib/css-plugin.js

@@ -41,6 +41,7 @@ const assetRe = new RegExp('/fake/path/to/asset/([^/]+)/', 'g');
 const appendCssModule = '\0appendCss';
 const appendCssSource = `
   export default function appendCss(css) {
+    if (__PRERENDER__) return;
     const style = document.createElement('style');
     style.textContent = css;
     document.head.append(style);