Addon-docs: Add support for Vue 3

[phated]

Issue: Follow up to #13775

What I did

I added initial support for Vue 3 in @storybook/addon-docs. This was mostly a copy-paste of the vue implementation, but the prepareForInline became very streamlined since Vue 3 allows you to render a vnode directly into the DOM.

Notably missing: The sourceDecorator from Vue 2 won't work because vnodes no longer contain all the information to build up the templates. I explored calling render(vnode, document.createElement('div')) before looking at the props and it helped a bit, but I think the true way to build this would be a custom renderer, similar to how they do SSR and their test utils. However, that is way out of my depth.

I also needed to fix the types in the html framework for some reason.

How to test

I tested this in the vue 3 example storybook and it seems to be working.

If your answer is yes to any of these, please make sure to include it in your PR.

[shilman]

LGTM 🥇

[Mootook]

@phated Perhaps I'm missing something but why is this still concerned with previous vue?

// addons/docs/src/frameworks/vue3/preset.ts
loader: require.resolve('vue-docgen-loader', { paths: [require.resolve('@storybook/vue')] })

since I get Error: Cannot find module '@storybook/vue' when running start-storybook -p 6006 using @storybook/vue3.

[phated]

@Mootook Just a bug. Good catch. A lot of this work was just copy-pasting the @storybook/vue code and adapting some parts to vue 3 APIs and I missed this reference. I'll submit a patch.