docs (#154): add new features section to migration guide (#161)

* docs (#154): add new features section to migration guide

* docs (#154): add createRenderer API as new feature for v3

Author: bencodezen

src/guide/migration.md

@@ -37,3 +37,13 @@ It depends on a few factors:
 > If I upgrade to Vue 3, will I also have to upgrade Vuex and Vue Router?
 
 [//]: # 'TODO: still need to see where this lands'
+
+### New Features
+
+Some of the new features to keep an eye on in Vue 3 include:
+
+- [Composition API](/guide/composition-api-introduction.html)
+- [Teleport](/guide/teleport)
+- Fragments
+- [Emits Component Option](/guide/component-custom-events.html)
+- `createRenderer` API from `@vue/runtime-core` to create custom renderers