Added custom "vanilla" renderer

You can now import the custom "vanilla" renderer from the @webtides/elemen-js/src/renderer/vanilla package.

This renderer does not use any external dependencies and can easily be renderered on the server and hydrated on the client.

Example:

import { TemplateElement, html } from "@webtides/element-js/src/renderer/vanilla";

export default class MyVanillaTemplateElement extends TemplateElement {
    template() {
        return html`
             This works.
        `;
    }
}