fix($docs): Update link to the 0.x documentation (#1852)

Author: kidonng

Diff for: packages/docs/docs/.vuepress/nav/en.js

@@ -69,6 +69,6 @@ module.exports = [
   },
   {
     text: "0.x",
-    link: "https://vuepress.vuejs.org/"
+    link: "https://v0.vuepress.vuejs.org/"
   }
 ];

Diff for: packages/docs/docs/.vuepress/nav/zh.js

@@ -69,6 +69,6 @@ module.exports = [
   },
   {
     text: "0.x",
-    link: "https://vuepress.vuejs.org/"
+    link: "https://v0.vuepress.vuejs.org/"
   }
 ];