feat: add links to migration build page

Author: yyx990803

src/.vuepress/config.js

@@ -171,6 +171,7 @@ const sidebar = {
   ],
   migration: [
     '/guide/migration/introduction',
+    '/guide/migration/migration-build',
     {
       title: 'Details',
       collapsable: false,

src/guide/migration/introduction.md

@@ -7,6 +7,7 @@ New to Vue.js? Check out our [Essentials Guide](/guide/introduction.html) to get
 This guide is primarily for users with prior Vue 2 experience who want to learn about the new features and changes in Vue 3. **This is not something you have to read from top to bottom before trying out Vue 3.** While it looks like a lot has changed, a lot of what you know and love about Vue is still the same; but we wanted to be as thorough as possible and provide detailed explanations and examples for every documented change.
 
 - [Quickstart](#quickstart)
+- [Migration Build](#migration-build)
 - [Notable New Features](#notable-new-features)
 - [Breaking Changes](#breaking-changes)
 - [Supporting Libraries](#supporting-libraries)
@@ -20,6 +21,8 @@ Start learning Vue 3 at [Vue Mastery](https://www.vuemastery.com/courses-path/vu
 
 ## Quickstart
 
+If you want to quickly try out Vue 3 in a new project:
+
 - Via CDN: `<script src="https://unpkg.com/vue@next"></script>`
 - In-browser playground on [Codepen](https://codepen.io/yyx990803/pen/OJNoaZL)
 - In-browser Sandbox on [CodeSandbox](https://v3.vue.new)
@@ -37,6 +40,10 @@ Start learning Vue 3 at [Vue Mastery](https://www.vuemastery.com/courses-path/vu
   # select vue 3 preset
   ```
 
+## Migration Build
+
+If you have an existing Vue 2 project or library that you intend to upgrade to Vue 3, we provide a build of Vue 3 that offers Vue 2 compatible APIs. Check out the [Migration Build](./migration-build.html) page for more details.
+
 ## Notable New Features
 
 Some of the new features to keep an eye on in Vue 3 include:
@@ -53,10 +60,6 @@ Some of the new features to keep an eye on in Vue 3 include:
 
 ## Breaking Changes
 
-::: info INFO
-We are still working on a dedicated Migration Build of Vue 3 with Vue 2 compatible behavior and runtime warnings of incompatible usage. If you are planning to migrate a non-trivial Vue 2 app, we strongly recommend waiting for the Migration Build for a smoother experience.
-:::
-
 The following consists a list of breaking changes from 2.x:
 
 ### Global API