fix(addon-docs): Handle object-in-array class (Vue.js)

https://vuejs.org/v2/guide/class-and-style.html#Array-Syntax

Add support for below.

```vue
<div v-bind:class="[{ active: isActive }, errorClass]"></div>
```

addons/docs/src/frameworks/vue/sourceDecorator.test.ts

@@ -64,30 +64,30 @@ describe('vnodeToString', () => {
     expect(
       vnodeToString(
         getVNode({
-          template: `<button :class="['foo', null, false, 0]">Button</button>`,
+          template: `<button :class="['foo', null, false, 0, {bar: true, baz: false}]">Button</button>`,
         })
       )
-    ).toMatchInlineSnapshot(`<button class="foo">Button</button>`);
+    ).toMatchInlineSnapshot(`<button class="foo bar">Button</button>`);
   });
 
-  it('merge dynamic and static classes', () => {
+  it('object dynamic class', () => {
     expect(
       vnodeToString(
         getVNode({
-          template: `<button class="foo" :class="{bar: null, baz: 1}">Button</button>`,
+          template: `<button :class="{foo: true, bar: false}">Button</button>`,
         })
       )
-    ).toMatchInlineSnapshot(`<button class="foo baz">Button</button>`);
+    ).toMatchInlineSnapshot(`<button class="foo">Button</button>`);
   });
 
-  it('object dynamic class', () => {
+  it('merge dynamic and static classes', () => {
     expect(
       vnodeToString(
         getVNode({
-          template: `<button :class="{foo: true, bar: false}">Button</button>`,
+          template: `<button class="foo" :class="{bar: null, baz: 1}">Button</button>`,
         })
       )
-    ).toMatchInlineSnapshot(`<button class="foo">Button</button>`);
+    ).toMatchInlineSnapshot(`<button class="foo baz">Button</button>`);
   });
 
   it('attributes', () => {

addons/docs/src/frameworks/vue/sourceDecorator.ts

@@ -76,7 +76,7 @@ export const sourceDecorator = (storyFn: any, context: StoryContext) => {
 export function vnodeToString(vnode: Vue.VNode): string {
   const attrString = [
     ...(vnode.data?.slot ? ([['slot', vnode.data.slot]] as [string, any][]) : []),
-    ['class', normalizeClassAttribute(vnode)],
+    ['class', stringifyClassAttribute(vnode)],
     ...(vnode.componentOptions?.propsData ? Object.entries(vnode.componentOptions.propsData) : []),
     ...(vnode.data?.attrs ? Object.entries(vnode.data.attrs) : []),
   ]
@@ -123,27 +123,41 @@ export function vnodeToString(vnode: Vue.VNode): string {
     .join('')}</${tag}>`;
 }
 
-function normalizeClassAttribute(vnode: Vue.VNode): string | undefined {
+function stringifyClassAttribute(vnode: Vue.VNode): string | undefined {
   if (!vnode.data || (!vnode.data.staticClass && !vnode.data.class)) {
     return undefined;
   }
 
-  let dynamicClass: readonly string[] = [];
+  return (
+    [...(vnode.data.staticClass?.split(' ') ?? []), ...normalizeClassBinding(vnode.data.class)]
+      .filter(Boolean)
+      .join(' ') || undefined
+  );
+}
 
-  if (typeof vnode.data.class === 'string') {
-    dynamicClass = [vnode.data.class];
-  } else if (vnode.data.class instanceof Array) {
-    dynamicClass = vnode.data.class;
-  } else if (typeof vnode.data.class === 'object') {
-    dynamicClass = Object.entries(vnode.data.class)
+// https://vuejs.org/v2/guide/class-and-style.html#Binding-HTML-Classes
+function normalizeClassBinding(binding: unknown): readonly string[] {
+  if (!binding) {
+    return [];
+  }
+
+  if (typeof binding === 'string') {
+    return [binding];
+  }
+
+  if (binding instanceof Array) {
+    // To handle an object-in-array binding smartly, we use recursion
+    return binding.map(normalizeClassBinding).reduce((a, b) => [...a, ...b], []);
+  }
+
+  if (typeof binding === 'object') {
+    return Object.entries(binding)
       .filter(([, active]) => !!active)
       .map(([className]) => className);
   }
 
-  return (
-    [...(vnode.data.staticClass?.split(' ') ?? []), ...dynamicClass].filter(Boolean).join(' ') ||
-    undefined
-  );
+  // Unknown class binding
+  return [];
 }
 
 function stringifyAttr(attrName: string, value?: any): string | null {