gizmo: dynamic loader

[unional]

const loader = (gizmos: Gizmo[], result: AnyRecord) => (identifier: string) => Promise<AnyRecord>

incubator().with(...).create(loader)

Only when there are dynamic dependencies.

UPDATE:

to work with #186:

incubator().with(...).create((gizmo, ctx) => {
  ctx.setDynamicLoader(...)
  return () => clean up
}

or

// only set once and remove from the chain
incubator().loader().with(...).create()

[unional]

There are 3 options to add the loader:

• before: incubate().loader({ ... }).with(...).create() - not preferred as there is no way to type the loader.
  (alternative incubate(init, { loader: { ... } }).with(...).create())
• after: incubate().with(...).loader({ ... }).create() - can type the loader, and can add loader along with the incubator. However, do not know what is the use case of adding loader with the incubator. And it makes the logic quite difficult, as now we need to exclude or able to override what's already in the incubator.
• on creation: incubate().with(...).create((g, ctx) => { ctx.setLoader({ ... }) }) - can type the loader. Down side is the loader need to be specified on every creation.