feat: add types to nebula serve

[Caele]

Motivation

Allows for the serve configuration to register extra types to the embed instance:

module.exports = {
  serve: {
    types: [{ name: 'barchart', url: "https://unpkg.com/@nebula.js/sn-bar-chart"}],
  },
};

This allows an chart to render the extra types using useEmbed.

Todo:

• Docs
• Tests?