feat($core): support passing in meta

Author: ulivz

packages/@vuepress/core/lib/internal-plugins/routes.js

@@ -33,13 +33,14 @@ function routesCode (pages) {
   function genRoute ({
     path: pagePath,
     key: componentName,
-    regularPath
+    regularPath,
+    _meta
   }) {
     let code = `
   {
     name: ${JSON.stringify(componentName)},
     path: ${JSON.stringify(pagePath)},
-    component: LayoutDistributor,
+    component: LayoutDistributor,${_meta ? `\n    meta: ${JSON.stringify(_meta)}` : ''}
   }`
 
     const dncodedPath = decodeURIComponent(pagePath)

packages/@vuepress/core/lib/prepare/Page.js

@@ -15,6 +15,7 @@ module.exports = class Page {
    */
   constructor ({
     path,
+    meta,
     title,
     content,
     filePath,
@@ -24,6 +25,7 @@ module.exports = class Page {
     permalinkPattern
   }) {
     this.title = title
+    this._meta = meta
     this._filePath = filePath
     this._content = content
     this._permalink = permalink