Merge pull request #6447 from backbone87/vue-sb5-migration

update migration.md with vue changes introduced in sb5

MIGRATION.md

@@ -14,6 +14,7 @@
   - [Addon a11y uses parameters](#addon-a11y-uses-parameters-decorator-renamed)
   - [New keyboard shortcuts defaults](#new-keyboard-shortcuts-defaults)
   - [New URL structure](#new-url-structure)
+  - [Vue integration](#vue-integration)
 - [From version 4.0.x to 4.1.x](#from-version-40x-to-41x)
   - [Private addon config](#private-addon-config)
   - [React 15.x](#react-15x)
@@ -191,7 +192,7 @@ Here is the mapping from old options to new:
 
 Storybook v5 removes the search dialog box in favor of a quick search in the navigation view, so `showSearchBox` has been removed.
 
-Storybook v5 introduce a new tool bar above the story view and you can show\hide it with the new `isToolshown` option. 
+Storybook v5 introduce a new tool bar above the story view and you can show\hide it with the new `isToolshown` option.
 
 ## Individual story decorators
 
@@ -351,6 +352,12 @@ https://url-of-storybook?path=/story/<storyId>
 
 The structure of `storyId` is a slugified `<selectedKind>--<selectedStory>` (slugified = lowercase, hyphen-separated). Each `storyId` must be unique. We plan to build more features into Storybook in upcoming versions based on this new structure.
 
+## Vue integration
+
+The Vue integration was updated, so that every story returned from a story or decorator function is now being normalized with `Vue.extend` **and** is being wrapped by a functional component. Returning a string from a story or decorator function is still supported and is treated as a component with the returned string as the template.
+
+Currently there is no recommended way of accessing the component options of a story inside a decorator.
+
 ## From version 4.0.x to 4.1.x
 
 There are are a few migrations you should be aware of in 4.1, including one unintentionally breaking change for advanced addon usage.