docs: document new features in 13.1.0 & 13.2.0

Author: yyx990803

docs/en/features/functioanl-template.md

@@ -0,0 +1,13 @@
+# Template for Functional Components
+
+> New in 13.1.0, requires Vue >= 2.5.0
+
+To denote a template that should be compiled as a functional component, add the `functional` attribute to the template block. This also allows omitting the `functional` option in the `<script>` block.
+
+Expressions in the template are evaluated in the [functional render context](https://vuejs.org/v2/guide/render-function.html#Functional-Components). This means props need to be accessed as `props.xxx` in the template:
+
+``` html
+<template functional>
+  <div>{{ props.foo }}</div>
+</template>
+```

docs/en/options.md

@@ -112,6 +112,21 @@ module.exports = {
   }
   ```
 
+### postcss.configRoot
+
+> New in 13.2.0
+
+- type: `string`
+- default: `process.cwd()`
+
+  Specify an alternative root directory for [postcss-load-config](https://github.com/michael-ciniawsky/postcss-load-config) to search for PostCSS config files in.
+
+  ``` js
+  postcss: {
+    configRoot: path.resolve('./src')
+  }
+  ```
+
 ### cssSourceMap
 
 - type: `boolean`
@@ -276,3 +291,12 @@ module.exports = {
 - default: `true` when the webpack config has `target: 'node'` and `vue-template-compiler` is at version 2.4.0 or above.
 
 Enable Vue 2.4 SSR compilation optimization that compiles part of the vdom trees returned by render functions into plain strings, which improves SSR performance. In some cases you might want to explicitly turn it off because the resulting render functions can only be used for SSR and cannot be used for client-side rendering or testing.
+
+### cacheBusting
+
+> New in 13.2.0
+
+- type: `boolean`
+- default: `true` in development mode, `false` in production mode.
+
+Whether generate source maps with cache busting by appending a hash query to the file name. Turning this off can help with source map debugging.