docs: update for 13.6.0

Author: yyx990803

docs/en/features/postcss.md

@@ -4,14 +4,25 @@ Any CSS output processed by `vue-loader` is piped through [PostCSS](https://gith
 
 ## Using a Config File
 
-Starting in 11.0 `vue-loader` supports auto-loading the same PostCss config files supported by [`postcss-loader`](https://github.com/postcss/postcss-loader#usage):
+`vue-loader` supports auto-loading the same PostCss config files supported by [`postcss-loader`](https://github.com/postcss/postcss-loader#usage):
 
 - `postcss.config.js`
 - `.postcssrc`
 - `postcss` field in `package.json`
 
 Using a config file allows you to share the same config between your normal CSS files processed by `postcss-loader` and the CSS inside `*.vue` files, and is recommended.
 
+## Using with `postcss-loader`
+
+Since `vue-loader` handles PostCSS on its styles internally, you only need to apply `postcss-loader` to standalone CSS files. There's no need to specify `lang="postcss"` on a style block if there is a PostCSS config file in your project.
+
+Sometimes the user may want to use `lang="postcss"` only for syntax highlighting purposes. Starting in 13.6.0, if no loader has been explicitly configured for the following common PostCSS extensions (via `vue-loader`'s own `loaders` option), they will simply go through `vue-loader`'s default PostCSS transforms:
+
+- `postcss`
+- `pcss`
+- `sugarss`
+- `sss`
+
 ## Inline Options
 
 Alternatively, you can specify postcss config specifically for `*.vue` files using the `postcss` option for `vue-loader`.
@@ -66,3 +77,17 @@ In addition to providing an Array of plugins, the `postcss` option also accepts:
     }
   }
   ```
+
+### Disabling Auto Config File Loading
+
+In `13.6.0+`, auto postcss config file loading can be disabled by specifying `postcss.useConfigFile: false`:
+
+``` js
+postcss: {
+  useConfigFile: false,
+  plugins: [/* ... */],
+  options: {/* ... */}
+}
+```
+
+This allows the postcss configuration inside `*.vue` files to be entirely controlled by the inline config.

docs/en/options.md

@@ -137,6 +137,15 @@ module.exports = {
 
     Provide context to PostCSS plugins. See [postcss-loader docs](https://github.com/postcss/postcss-loader#context-ctx) for more details.
 
+### postcss.useConfigFile
+
+> New in 13.6.0
+
+- type: `boolean`
+- default: `true`
+
+  Set this to `false` to disable auto-loading of postcss config files.
+
 ### cssSourceMap
 
 - type: `boolean`