Add JSX support and a vanilla JS API

[Daniel Dietrich]

Update: we need to distinguish this issue into two tasks:

• [🙅‍♀️ wontfix] there exist JSX DOM factories on npmjs.com, we do not ship them as part of candid. The JSX binding is part of the runtime env, not of the Candid lib.
• provide a function to programmatically define web-components

type Options = {
  mode?: 'open' | 'closed' | null // shadow root mode (default: null)
  extends?: string | null // super tag name (default: null)
  props?: object | null // observed properties and default values
  template?: HTMLTemplateElement | null //  the html template
}

// Candid.createWebComponent()
function createWebComponent(name: string, options?: Options)

Question: Should createWebComponent() call customElements.define()?

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Currently we use a declarative approach only and only have one public API candid(options) to initialize Candid.

We should think about exposing the JS API in order to allow to create web-components dynamically using JS. Maybe it also makes sense to expose the web-import API.

It is not sufficient to just export existing functions. Most probably we might need to re-design the internal API.

See also Write your own DOM element factory for TypeScript.