add: vuepress plugin config

Author: dongyuanxin

comment.js

@@ -0,0 +1,5 @@
+import Comment from './Comment.vue'
+
+export default ({ Vue }) => {
+  Vue.component('Comment', Comment)
+}

index.js

@@ -0,0 +1,13 @@
+const path = require('path')
+
+module.exports = (opts, ctx) => {
+  return {
+    define: {
+      COMMENT_CHOOSEN: opts.choosen || 'gitalk',
+      COMMENT_OPTIONS: opts.options || {},
+      COMMENT_CONTAINER: opts.container || 'main.page'
+    },
+    enhanceAppFiles: path.resolve(__dirname, 'comment.js'),
+    globalUIComponents: 'Comment'
+  }
+}