message: improved docs for css plugin
diff: @@ -11,11 +11,12 @@ import css from "https://deno.land/x/lume/plugins/css.js";
  site.use(css());
  ```
  -This plugin loads CSS files and use [PostCSS](https://postcss.org/) with [postcss-preset-env](https://preset-env.cssdb.org/) to transform the code so most browsers can understand (adding polyfills for modern features, autoprefixer, etc). It also resolve the local `@imports` with relative urls. For example:
  +This plugin loads CSS files and use [PostCSS](https://postcss.org/) with [postcss-preset-env](https://preset-env.cssdb.org/) to transform the code so most browsers can understand (adding polyfills for modern features, autoprefixer, etc). It also resolve the local `@imports` with relative urls using [postcss_import](https://deno.land/x/postcss_import) plugin, looking in the `_includes` folder.
  ```css
  -@import "./_includes/reset.css";
  -@import "./_includes/variables.css";
  -@import "./_includes/components/button.css";
  -@import "./_includes/components/input.css";
  +/* Import the css file from _includes/css/reset.css */
  +@import "css/reset.css";
  +
  +/* Import the relative css file */
  +@import "./variables.css";
  ```
  \ No newline at end of file
  