feat: integrate with feed (#58)

Author: billyyyyy3320

docs/config/README.md

@@ -249,4 +249,18 @@ It will be enabled when `endpoint` is provided. e.g.
 ```
 [vuepress-plugin-mailchimp](https://vuepress-plugin-mailchimp.billyyyyy3320.com/) is how we implement the feature. This config will be pass directly to it, so please head [vuepress-plugin-mailchimp](https://vuepress-plugin-mailchimp.billyyyyy3320.com/#config) for more details.  
 
+## feed
 
+- Type: `object`
+- Default: `{}`
+- Required: `false`
+
+It will be enabled when `canonical_base` is provided. e.g.
+
+```js
+{
+  canonical_base: 'https://yoursite'
+}
+```
+
+All the generated files will be placed under your output directory. If you wish to make further configuration, please check out [vuepress-plugin-feed](https://github.com/webmasterish/vuepress-plugin-feed).

docs/guide/getting-started.md

@@ -460,6 +460,29 @@ In your theme, You'll probably offer users options whether to enable or not. You
 
 Please head [UI-customization](https://vuepress-plugin-mailchimp.billyyyyy3320.com/#ui-customization) if you don't like the default UI.
 
+## Feed
+
+Feed is another approach to allow your users to get your latest content. RSS, Atom, and even JSON feeds are the right tools for the job. Let's see an example:
+
+```JavaScript
+// .vuepress/config.js
+module.exports = {
+  plugins: [
+    [
+      '@vuepress/blog',
+      {
+        feed: {
+         canonical_base: 'http://yoursite',
+        },
+      },
+    ],
+  ],
+}
+```
+
+After building, you'll be able to find them (`rss.xml`, `feed.atom`, `feed.json`) in you output directory (`dist`).
+
+
 ## Examples
 
 There're some [examples](https://github.com/vuepressjs/vuepress-plugin-blog/tree/master/examples) under this project help us test this plugin. They're also simplest examples for you after reading all the concept above. 

examples/sitemap/.vuepress/config.js renamed to examples/sitemap+feed/.vuepress/config.js

@@ -26,6 +26,9 @@ module.exports = {
       sitemap: {
         hostname: 'https://yourdomain'
       },
+      feed:{
+        canonical_base: 'http://localhost:8080',
+      }
     }],
   ],
 }