[feat]: support `package.json` e.g via `pkg.template`

[michael-ciniawsky]

{
    name: "component",
    version: "1.0.0",
    main: "lib/component.js", 
    style: "lib/component.css",  // postcss-import
    template: "lib/component.html", // posthtml-include <=
}

[Scrum]

@michael-ciniawsky Need more examples to understand the need for this