message: Add `postcss` filter
diff: @@ -37,6 +37,7 @@ export default function (userOptions = {}) {
  site.loadAssets(options.extensions, textLoader);
  site.process(options.extensions, processor);
  + site.filter("postcss", filter, true);
  async function processor(page) {
  const from = site.src(page.src.path + page.src.ext);
  @@ -55,5 +56,10 @@ export default function (userOptions = {}) {
  site.pages.push(mapFile);
  }
  }
  +
  + async function filter(code) {
  + const result = await runner.process(code, { from: undefined });
  + return result.css;
  + }
  };
  }
  