feat(types): add DOM type definition for JSX element

[andoshin11]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

Descriptions

• Inspired by vue-tsx-support by @wonderful-panda who was also inspired by @types/react
• This PR is not aiming for perfection. I'd love to hear feedbacks from Vue core team as this is my very first PR.

By providing officially maintained HTML Attributes Types, developers can get a huge benefit when they are writing TSX.

All you need is just a few tweaks on shims-tsx.d.ts

// shims-tsx.d.ts
import Vue, { VNode, VIntrinsicElementAttributes } from 'vue'

declare global {
  namespace JSX {
    // tslint:disable no-empty-interface
    interface Element extends VNode {}
    // tslint:disable no-empty-interface
    interface ElementClass extends Vue {}
    interface IntrinsicElements extends VIntrinsicElementAttributes {
      [elem: string]: any
    }
  }
}

[kazupon]

@andoshin11
Thank you for your PR!
It looks nice to me, but it looks like it should be provided in other ways (e.g. Vue CLI plugin), not Vue Core.

@ktsn @HerringtonDarkholme
What do you think?

[HerringtonDarkholme]

I think this is a nice add. However I agree with @kazupon this change is not suitable to be included in Vue's core repo. The reason is that dom definition alone cannot provide tsx improvement by default: users have to include shim-tsx.d.ts manually.

My point is if we want to include the dom definition for tsx, we should support tsx support at core repo at first (which is already scheduled in Vue 3). Otherwise this change is better to reside in tsx-support library. @ktsn any opinion?

[ktsn]

I think it is fine to include this in core repo now as we'll do that sooner or later. We can update shim-tsx.d.ts in Vue CLI template to use the dom types until we support it by default.